WANTED – Ideas for a new type of zombie

7th July 2018

This is an Idea Challenge. The first of its kind for RTSL. Suggested by Mr. Mazur.

Earlier today, I tweeted this:

The upshot was that I realised we should be creating a new zombie class that uses the MechaCrab zombie. If you don’t know what the MeachCrab zombie is, please visit the RTSl Mod Template page.

We feel that the MechaCrab should be attached to the Rebel model, as that model doesn’t have an official zombie type. But that is not set in stone, we could change that.

Idea Challenge

Therefore, I would like to hear your suggestions for a zombie based on the MechaCrab. We need sensible ideas that can be coded and modelled. Ideas that fit into the HL Universe, so don’t suggest things like the MechaCrab on the G-Man, for instance.

We require some unique features for its attack. Something that makes it feel fresh, different AND fun to play against.

Of course, we will have to beta test things but this challenge is just about the ideas.

I know that there are probably lots of new types of zombies on Steam Community and Game Banana, but I don’t want to use soemthign that has already been created.

I will give some games away to the best ideas.

Submission Rules

There’s only three rules:
1. By submitting you idea, you grant RTSL the right to create and release the concept as part of the RTSL Mod Template.
2. You are the creator of the idea.
3. It’s family friendly, within the confines of the Half-Life 2 setting.

Post your ideas as a comment below or if you want to do it privately, then send an email to [email protected]

Let me know if you have any questions.


  1. Can we inspire from something else? not related with zombies

    1. Yes, I think. I might need to see what your idea is first.

      1. where can i submit my idea?

        1. Here. As a comment, unless you want to do it privately, then send an email to [email protected]

      2. submitted hope you like it

  2. Instead of a Headcrab how about Asscrabs? Crabs that infect the host by entering via the anus. When the infected host is killed with a shotgun blast for example the Asscrab can launch from the butt with hilarious results.

    1. Trust you to suggest something like that.

  3. – Mechazombie grow a metal shield on its arm it can use to defend itself and deflect bullets/sawblades.
    – Mechazombies are living generator and deal electricity based area of effect attacks. Protip: don’t go near water if there is one nearby. Protip 2: kill the mechazombie to power down nearby forcefields.
    – Mechaheadcrabs can leap out of their host at great distance.
    – Mechaheadcrabs needs a stalker as a host. The mechazombie can use the stalker laser.
    – Mechaheadcrabs can grow a bomb in their host. Mechazombies act as a suicide bomber.

    These are several ideas, I’m not suggesting to implement all of them. Choose one.

  4. If at all possible I thought it could be quite cool to incorporate the old Half Life 2 Beta Zombie Assassins using the MechaCrab.

    I quickly made 2 concept images using the MechaCrab and the Zombie Assassin images:

    Unarmoured Variant:

    Armoured Variant:

    I thought seeing as the MechaCrab has increased speed, damage and armour this would carry over to the zombie itself like how the Fast Headcrabs create Fast Zombies.

  5. Xblah

    Something that would be nice was to use the Mecha headcrab in the zombie as a laser pointer for Headcrab cannisters. It would need some scripting in the map, but mecha zombies could wander around and if they spot a possible “host” for other headcrabs, it would call a headcrab cannister in the spot.

  6. Firstly, I’m hesitant about introducing the Mechazombie as a high-health tank. The increased health of the Mechacrab doesn’t seem to be a widespread favourite in the community, but more importantly the poison zombie already fills the niche of a meat wall.

    I really like the suggestion Klems had of introducing a type of shield to the enemy which would block damage, so long as the base health of the npc isn’t artificially inflated.
    My first suggestion would be:
    – Very durable, or damage immune, from the front
    – Has a weak point on his back which kills him fast if shot. Explosives could bypass this.
    – Increased melee damage
    – Slow turning speed
    If any of you played the “Outbreak” mode a few months ago in Rainbow 6 Siege, there was an enemy that was very similar, perhaps it could charge like a bull, becoming stunned and vulnerable should it strike a wall.

    I also support the idea of the electricity/EMP version. Using it to disable forcefields is a really compelling key-door system.
    However, I think poison zombies and zombines already fulfill the role of area denial very well, they force players out of areas and require them to traverse parts of the map during that retreat, usually into other enemies.
    Currently no zombie really applies pressure to the player at range, distancing yourself from the enemy is usually the best answer, particularly with zombines. Poison zombies remedy the ranged capability of the zombies somewhat, but can still be easily dodged through running away.
    Therefore my second idea is:
    – Can fire a small laser projectile, in a burst of three. This is a hitscan which deals very low damage, say around 2-5 per shot, and requires a moment to recharge between bursts. Has an activation period and alarm like combine turrets.
    Can climb up pipes like a fast zombie, but pause at set points. From here is acts like a static turret in midair, clinging to the pipe.


    – Buffs enemies in some form, e.g. shields, bonus speed and damage, in an area around it. This would encourage, but not force, the player to seek out this “commander” type enemy before tackling other zombies. This would ideally create a departure from the “just shoot the closest zombie” gameplay.

    Thirdly, the zombie could be made different from other enemies by subverting the common ways of dealing with zombies:
    – Fire
    – Explosives
    – GGun projectiles
    Whilst this could be a pretty wonky idea to implement, my third idea is:
    – Radiates pulses of energy which knocks players and physics objects away, radially. This means the player has to find a way to deal with this in order to cleanly use grenades or physics objects to attack zombies behind him. I like the idea that a well aimed grenade or explosive object can still be useful, the area does not ‘delete’ the projectile, but merely alter its course in a fairly predictable way.

    Finally, something that enhances it’s ability to be a spooky/horror enemy. The tricks zombies have are quite limiting in evoking a startling response as we’ve become accustomed to what a zombie looks like in the sleeping/slump position.
    I wanted to therefore introduce a paranoia aspect to dealing with MechaZombies. My last idea is:
    – Largely increased melee damage
    – Short range zombine sprint
    – Plays a distinct audio sound, as an ambient drone, to warn the players it is nearby. This is louder the closer you are. The more unsettling the sound, the better.
    – Visually difficult to see due to being ‘cloaked’, and/or can affix itself to ceilings and high walls where it waits in ambush. This requires the player to check all angles in a room rather than just the floor, and use the sound queues to locate. Perhaps this could be used to help highlight areas above the player they might miss.
    If cloaked, the sound could be used to isolate where the enemy is. This is not required though, the zombie reveals itself if the player gets near enough to attack, it cannot move and stay hidden.

    How any of these could be justified in lore, I’m very unsure. Perhaps the MechaCrab could be visually consuming the host to power it’s enhanced tech? The host could visibly writhe and flinch when a tech ability is used.
    These ideas are probably a bit over the top and tough to implement, simpler ideas, such as Klems’ suggestion of having the MechaCrab survive the host being killed far more often, or sacrificing the host at will to jump at the player, might be more feasible in implementation and having the player understand what to do against them.

    1. Thanks for the detailed response. We are thinking carefully about the “ranged” attack.

  7. Unknown

    What about their blood as being toxic. The problem with the zombie blood is it doesn’t show-up all that often. I wish it had more clarity. Like maybe instead when you kill a zombie it disintegrates into a puddle of green goo that is toxic to the player. You could even add a slip and slide feature too it as well like if you stepped on an oil slick.

    Maybe if you hit them you would see a small blood trickle come out of them. I think that would be a more interesting feature to add. What about their placement as well. Like being able to stick to walls and run across walls like a real spider then you would be attacked in random areas you walk into a building seeing nothing is a miss only for a headcrab to drop down on to you and attack you.

    You could always code an idle mode for them. Similar to when the houndeyes all sleep. This would add a stealth aspect if you wish to sneak past them.

    Another idea I had is I noticed headcrabs they can create holes. This function wasn’t utilized all that much in the game, so perhaps they should also have this option as well. Maybe place them in areas you wouldn’t suspect. Like maybe when they go to sleep the wrap their limbs around a tree branch and if disturb they jump off and attack. You could even give them a quirkiness to them. Maybe they see a health kit laying on the ground and they can grab it and run away with it having you to have to run down and chance them to heal yourself.

  8. Unknown

    What about the design of the Mech Zombie. How you would kill it. I noticed that the headcrab zombies have those gaping stomachs, so maybe the armor would in case around the body leaving the stomach open. Maybe you would have to shot a grenade into the stomach to actually defeat the zombie. Maybe you would need to use a fire canister to implode inside the stomach causing flames to burst from out the headcrab. You could even use the similar swallowing function as the Barnacle uses if the code can be adjusted.

    You can even change the dynamics. Maybe you need the gravity gun to rip off the metal armor exposing it’s weak spots and maybe it’s difficult to remove. You may need to walk far enough for the armor to be fully pulled off piece by piece. Rip one sheet of metal off and then shot a saw blade at it’s stomach. Maybe their is 4 or 5 different metal plates you have to rip off. Eventually once you have hit the headcrab zombie with 4 or 5 saw blades it gets decapitated.

    1. Using the GGun to rip off armour is a really cool idea actually, I could see it retrofitting into any concept as an additional way to deal with the monster (i.e, have the armour rip mechanic on it’s own, or combine it with another new mechanic)
      It’ll certainly reward and encourage use of the GGun in zombie areas as opposed to the shotgun, which I think makes for a more interesting experience.

  9. Unknown

    Another thing I would like to bring-up as well. I have noticed when the headcrab zombies are on fire the fire doesn’t seem to damage you when they touch you which you figure it would. Just though I should point that out. Maybe there is a risk you could catch fire and maybe you have to sprint 2 or 3 times to put the fire out.

    Another coding option could be. Have you noticed zombies don’t pickup and throw items, but Dog has a throwing animation. Have them throw explosive barrels at you.

    Another attack option would be maybe you need to place barrel in-front of the headcrab zombie. Then you would have to run behind it and use the gravity gun. The magnetism from the armor would conduct the explosive barrel for I dunno a minute. So you would have a minute or 30 seconds to shot the barrel removing the armor of the headcrab zombie.

    A Gorey, but cool death would be if you take away all the headcrab zombie’s health a pool of blood would gush out of the stomach area when it dies. Maybe since it’s wearing armor when it explodes the metal shrapnel would go everywhere having the chance to impale you. The gibs can be different upon death as well. When you kill the headcrab zombie it vomits out some of the original organs like the heart, lungs or eyes.

  10. Anon_1673943

    Maybe we are all thinking just too small, after 20 years, having done HL 1, 2, 2.1 and 2.2 we need a complete make over (even a new engine)…we’ve been there, done it. Now that will probably upset the purists, but why does it have to be Half-Life ? in that universe ?…Eastern Europe does have it’s attractions ( I know, I live there), but what was the rest of the world doing while all this was going on ? What happened to all the other fighting forces globally ? We never find out. Yes, we could keep tweaking what we have (and do) but I think there’s a bigger story to tell, new enemies to add, situations to overcome…I’ve been looking around for something similar to play for a while now, with no success, keep it simple, no complicated key bindings but as much fun. I wonder what a head crab attached to a Hunter would produce, I’ve no idea but I’m not sticking around to find out…

  11. Corvatile

    I think it would be cool to see a stalker headcrab zombie. Maybe it could malfunction and have an effect on electronics around it;

    – Cause Combine forcefields to flicker or short circuit so the zombie horde can get through
    – Cause turrets or hopper mines to deactivate
    – Cause lights to break or temporarily darken
    – Cause Gordon’s flashlight to flicker

    Maybe when it dies it could collapse and shoot the laser from its eyes and incinerate the headcrab while trying to hit its enemy.

  12. PhilosophyZombie- Basically a normal zombie, but instead of zombie sounds, it shouts existential quotes at you, making you doubt your existence.

    StalkerZombies – Headcrabs infecting a Stalker (which are still somewhat human enough to be converted). Its weaker but more agile, using the hooks on its limbs to hang on to walls and ceilings.

    EliteZombine – Basically a zombine for Combine elites, but instead of a grenade kamikaze, it hangs on to its AR2, which it uses to fire a Combine energy ball at you on occasion, basically a long range one.

    1. Speaking of Mechaheadcrabs, seeing as synths are basically subjugated species that have been taken apart and rebuilt back by the Combine, So are Synth Headcrabs and a Synth Gonarchs a thing?

      Or maybe the Combine may have tried to make a headcrab-like mechanical unit (not a headcrab but a copy) that would try to drill itself into the victim’s cranium.

  13. Wesp5

    Sorry, but yet another zombie? The variety of enemies was one big drawback of HL2 compared to HL1! Instead of all the fantastic HL1 aliens, especially including those of Opposing Force, we only got three kind of headcrabs, three kind of zombies, three kind of combines, three kind of antlions… boring! Also I didn’t really like the mechaheadcrab in the first place and always assumed that it was just a normal slow headcrab stuck into some armor by the combine and that it would not have any special effects.

  14. Darlaimerner

    Deteriorating Zombie

    When this zombie attacks you, causes your health to slowly drain for 20 health (added to the damage the impact does) deterioration can be stopped if you take a health kit or battery.

    Zombie is slightly slower than a normal zombie, but can sprint like a zombine if injured too greatly.

    Headcrab looks like a rotting, greyish headcrab– something like a mix between a normal headcrab and a poison headcrab.

    If the deterorant headcrab hits you, does the same 20 DOT that a zombie does.

  15. CW3D
    MechaZombie (aka Flusher)


    Imagine this zombie basically being a Gonome (from half-life opposing force), except has more health, deals more damage, is able to leap/jump to high or otherwise in accessible places, is about as big as a Hunter (maybe bigger) and is much more scarier! O_o

    Still is able to throw acid at you (like a Gonome), but only has a certain amount to throw at the player. The more is throws at you, the weaker it gets (still pretty tough at its weakest though).

    Here’s some photos of what it could possibly look like: http://combineoverwiki.net/images/3/34/Zombie_Assassin_model.jpg

    if you combine the looks of them, that’s kinda what I imagine it looking like
    there is a more “detailed” description of them bellow

    [Back Story]

    The MechaZombie (Flusher) is a zombie that was created by the combine with the use of the MechaCrab. This zombie’s purpose for the combine is to clear and flush out certain sectors with brute and at times uncontrollable force which have been noted to either:

    A) Contain extreme Biotic and Necrotic overrun in an area that is deemed too much for the combine soldiers to handle themselves

    B) Contain high numbers of resistance members in an area that is deemed too much for the combine soldiers to handle themselves

    The MechZombie (Flusher) is also an experiment on how the combine can modify certain features of the MechaCrab to modify certain features of the crab’s host. Experimentation so far has been a success, however certain unintended features of the host’s body have been noted, which include:

    A) Possibly infectious black and bubbly blob growth spots near the host’s chest and smaller ones scattered around various parts of the body

    B) Various body parts have a metal plating growth (possibly from the MechaCrab’s metal extensions) to give extra defense and protection to the host

    C) All hosts’ pointer and pinky fingers have grown excessively longer than the rest of the fingers

    D) All hosts’ have had abnormal growth to a majority of their body parts, while certain other parts (like toes) have molded together

    E) All hosts’ have had certain parts of the bodies’ skin and muscle deteriorate and fall off (parts of the arm)

    No misbehavior from the MechaZombie (Flusher) has been noted, however signs of unresponsiveness have been noted.

  16. I’m excited about this idea challenge. I started thinking about it and I have a few ideas. Instead of just writing up a post, I’d like to map illustrating some of the concepts I have using existing NPCs. I’ll make a map and probably a video demonstrating how I think the mecha-zombie should work. Unfortunately, I can’t dedicate any time to this until my BossVille entry is completed. So I’ll probably work on it in about two weeks and then post what I make here. In the meantime I’m gonna try to avoid reading any more ideas from this page – it’s tempting though, I’m really curious.

  17. I’ve been reading some comments, and while some are very interesting of a coding challenge, it escapes the continuum of something biologically `natural` or possible. Having zombie become magnetic or electroactive in their own will starts knocking on something i’d see out of place in hl2, metal shield is also a little far fetched because an organism that is synthetically designed to just be a better headcrab won’t make sense on how this metal shield will grow out from the host as a tumor that you can interact with the gravity gun. If anything, a combine soldier carrying a energy shield that you have to remove with the GG is more feasible than having an organism get a host to develop metal growths.

    Mecha Zombie

    We have to not forget that mechacrabs are still under combine control, so their zombies will be too. But I want something simple for mecha zombies, like have immunity to be not attacked by wild headcrab zombies and direct the attention of them to the !player or rebel faction. So if a mecha zombie is deployed, it will get the rest of the natural zombies to just attack you and ignore the combine forces in the area. To me it always felt unfulfilling that combine soldiers attacked what was closest to them from areas inaccessible by zombies and not just attack the enemy that is able to fire back at them (i.e !player or rebels). In this case you have zombies and combine working with you to flush you out or move you from cover. Coding wise this is really easy and it can fulfill the hl2 canon of combine giving the mechaheadcrab pheromones or communicators for one of their mechacrab zombies act as a coordinator for the rest of the zombies.

    Another idea is for having the mechacrab be able to detach if the host is one fire or in an environment that will surely kill it(water too).

    Mechacrab zombies can also act as combine detectors that are part of a combine squad which soldiers or metrocops be able to come and investigate as soon as a mechacrab zombie sees a !player or an antlion or a rebel.

    I also really liked the idea of having a mechacrab zombie designate headcrab canister coordinates, it would mean that the player has to dispatch them to preserve a location being spammed by headcrabs, but coding wise and engine wise this could cause bottlenecks. As a scripted sequence, it’s fine.

    If you want to go with the fast zombie base for the mechacrab like assassins as people suggested, it would just fill the role of a better fast zombie with bigger parameters for their stats. Appending things like guns or having ambush behavior like standing on the ceiling in slump mode doesn’t quite gonna caught on the surprise element because it might make it look stupid.
    All depends if you just code it to slump upside-down on a ceiling.

    A gun appendage can work, but in that case it’s more to do that the mechacrab zombie itself is biologically engineered to control a body mass with gun appendages or mechanical tools, so you could make that fly for hl2 canon but retain it to not appear as much in future mapping challenges.

    I’d very much like a stalker zombie, but a normal plain headcrab can do that job and have it be believable than a mechacrab, since we have to remember mechacrabs are under combine control and have no reason to attack their own forces(unless you explain in the map why mechacrabs are hostile to combine…)

  18. I would suggest that this zombie has an smarter AI: he seeks cover when shot from the distance and also when there are nearby allies(enemies for the player) who are not attacking the player, so he cooperrates with allies. He moves slightly faster than the player can walk, and he can throw physik objekts better than the default zombie, he can take small objects with him to throw at the player.

  19. Dolbaeb101

    The headcrabs armor would make the zombie immune to headshots. It uses fast, low damage attacks (like the fast zombie) which heals the host by draining the players suit. As for the looks maybe have some sort of wires going out of the headcrab and down the host’s arms that would do the “absorption”

  20. Anon_1675760

    Why not the G-Man with a mecha head crab as the final boss, he’s frustratingly difficult to get your hands on, despite his normally cameo appearances he could put a bit more effort in…

  21. So I was thinking stalkers, too, but apparently pretty much everybody had that idea, too, so I had to come up with something else…

    Think about this: whatever beast you take, pretty much every enemy from Half-Life¬≤ can be killed with fire. Zombies, headcrabs, Combine, you name it. So for a mechacrab zombie, I’d imagine an enemy that is immune to fire.

    Now, you said it could fit on the rebel model, so let’s just for a second picture a rebel. We know they have mechanics etc, so I’d say, take a rebel, put a mechacrab on his head, and give him a blowtorch. Beta-Colonel Odessa Cubbage-like. What do we get? A fire-resistant zombie that can and will light you on fire. That’d be rad, I think.

    Another idea I had was electricity. That crab is part mechanic, so it’s reasonable to assume it’s somehow powered. Now, I wouldn’t go as far as saying the crab would grow its host limbs of metal, as some suggested, but what about cables? I’d like to see, say, wires sticking out of its hands, perhaps… the zombie would start sparking as soon as alerted and aware to an enemy’s presence and cause electrical harm. Still immune to fire, at best. That’d make for wholly new gameplay – imagine a mech zombie inside a horde of stock zombies, it sees you, gets nasty and this way electrocutes anything in its way, fellow zombie or player.

    Last but not least, I thought – the mech crab looks pretty combine and sophisticated enough to contain some more complicated circuits. What if it has enough combine technology in it to be able to pass through combine force fields? They’re designed to keep out non-combine lifeforms. I have a picture in my head right now of such a zombie passing through a force field, perhaps glowing in that way itself if that’s possible, code-wise. Since that’s a pretty strong skill, it could have the drawback of being sensitive to electricity. So it could walk through combine fences, but contact with electrical damage (wires etc) could, while not harming it, stun it for a few moments as its circuits overload.

    I hope there’s at least some useful concepts or ideas in here, I’d love to see parts of this used for the final NPC or mixed with other concepts!

  22. asterixer

    The Idea of a new enemy is cool, but the problem is:
    If we add new enemys to the game, these enemys dont show up under Linux or OSX, except someone will add it to the Linux and OSX Versions of the client and server bin files.

    So the more new Enemys will be added to the game, the less fun it will be to play it under non Windows OS’s

    If i had enough skills to change this i would but i can only write some scripts…

  23. I suppose I’ll throw my two cents in.

    Armored Zombine

    + Head and Body Armor (cannot take bullet or direct physics damage, immune to headshots, can only be sliced in half, blown up, and set on fire…arguably can be crossbow bolted and/or AR2-balled.)
    + Charges when provoked (similar to the Zombine charge behavior)
    + Slow claw attack, medium damage, but has greater knockback

    – Incapable of grenade suicide-bombing, seen by their impulsive Zombine counterpart.
    – No torso variant (it’s hard enough to kill it the first time!)

    +/- Consider a makeshift rebel-themed armored zombie as well.

    My aim with this zombie variant is to encourage players and designers alike to use more satisfying methods of dealing with zombies. Explosives, saw blades, and pyromania are all exciting ways to deal with zombies. Let’s face it, after crowbarring or 9mm pistol-ing your hundreth zombie to death in the beginning of a custom level it does start to get boring.
    At the same time, this zombie variant can also intentionally serve as a big obstacle to underequipped players. If guns and bullets are all you’ve got, then you’re going to have to flee from this zombie until you have the tools (gravity gun / explosives / flares …) to take care of it. The poison zombie was supposed to be considered a “tanky” enemy that gets more dangerous the longer it’s alive, but a few shotgun blasts can dispatch it rather quickly! The armored zombine, however, can be fast, deadly, and hard to kill. It should be noted that the use of these zombies should be sparse, sort of like how Hunters are used. Finally, a reason for new players and seasoned veterans alike to get scared of zombies once again!

    Acid Zombie

    + Attacks deal neurotoxin damage (harsh at first but health regenerates over time)
    + Explodes in a spectacle of acid when killed, enemies of all variants are harmed in its radius.
    + Resistant to the acidic attacks from Antlion Workers and other Acid Zombies.
    + Barnacles will be killed when attempting to consume this zombie.
    + Neurotoxin-laced attacks deal extra damage to enemies other than the player, particularly antlions, combine soldiers, and humans.

    – Distinct glow makes this enemy stand out from the crowd
    – Entire crowds of zombies can be harmed or killed from this enemy’s explosion

    Inspired by the Antlion Worker and those pesky Boomers and Spitters from Left 4 Dead, the Acid Zombie puts a dangerous new spin on fighting zombies. Now players will think twice before getting up close with their shotgun, and they might even have to think a third time if there’s something important near the acid zombie. Getting hit by this glowing guy is a bad idea, because you’d be hit by neurotoxin as well. Good thing your suit treats you well, though, because your health will regenerate over time. Don’t worry too much about it…you won’t be brought down to a single point of health like those pesky black headcrabs. Just play it cool, slow down, and you should make it out of the fight without any burning holes in your skin.

    Feel free to tack on your own suggestions, and thank you for reading!

  24. I created a video demonstrating a few of these comments to go along with my post: https://youtu.be/xacFDdQd-Ls


    As a Combine unit, the mecha-zombie should synergize with the existing Combine forces. It can do this by forming a squad with Combine Soldiers and using the same ‘squad slots’ as existing Combine soldiers. To match pace with Combine soldiers, it must have a faster walking speed than the standard zombies. Additionally, slightly higher hitpoints than a standard zombie (but not significantly higher) and a higher resistance to headshots would help make it a worthwhile support / distraction unit.

    AI Design

    Combine tactics are based around the concept of ‘squad slots’. In order to perform an action, a Combine must reserve a squad slot, but only one soldier in the squad can reserve that slot at a time. There are two attack slots, meaning that two soldiers may shoot while the rest of the squad is forced to flank or take cover. The mecha-zombie should be able to use Combine soldier squad slots. While it is attacking the player, if the mecha-zombie is in a squad with Combine soldiers, only one soldier may shoot at the player, allowing the rest of the squad more time to flank the player’s position. SMG soldiers are very ineffective at long range, so buying them time to close in on the player will increase their lethality.

    The dynamic of using Combine squad slots has a side effect that if only mecha-zombies are in a squad together, only two of them may attack the player with a melee attack at the same time. This is beneficial for a few reasons. If a mapper uses a large number of mecha-zombies in one area, rather than overwhelm the player at once, they will ‘take turns’ attacking. While not attacking, the mecha-zombies should ‘hide’, creating small ambushes for the player. They can do this by retreating for cover, a behavior more commonly associated with the Combine soldier. Since they cannot ‘duck’ in cover the way a soldier would, they should exclusively seek cover by trying to break line of sight with the player. In large open arenas this may be difficult; they should instead attempt to ‘flank’ the player by moving behind Gordon’s field of view and then waiting for an attack slot to open.

    Another effective way to synergize with Combine soldiers is to act as a ‘meat shield’ for advancing soldiers. (I demonstrated this using Hammer by creating an ai_goal_follow entity that causes a shotgun soldier to ‘follow’ a Zombine) If the mecha-zombies can interrupt the player’s line of sight to advancing soldiers, this will buy the soldiers more time to flank the player. If the Combine soldier is equipped with an AR2 or is firing from cover, this behavior might have the reverse effect of protecting the player from a ranged attack. This can be avoided programmatically if mecha-zombies will not try to protect AR2 soldiers or soldiers in cover.

    Relationship with Regular Zombies / Headcrabs

    I would like to suggest a change to the standard mecha-headcrab as well as a feature for the mecha-zombie. Mecha-headcrabs and mecha-zombies should be hostile towards standard headcrabs and standard zombies, but only if they are in a squad with a Combine unit or if the nearby standard headcrabs and zombies are not in combat with Combine units. Rationally, it would make sense for the Combine not to force mecha-headcrabs to attack other headcrabs unless they had a practical reason to do so, IE they need to clear the headcrabs out of an area so Combine soldiers can proceed without any risk of being turned into Zombine. This behavior should also be configurable in hammer so that mappers can choose to make mecha-headcrabs always friendly towards other headcrabs or always hostile, or to decide dynamically based on nearby Combine units. Worst case, all of these behaviors can be replicated in hammer using ai_relationship entities, but providing this functionality to mappers in the entity itself will make mapping with mecha-headcrabs easier.

    NPC behavior should be predictable by the player based only on appearance. If the relationships between mecha-headcrabs / mecha-zombies and other NPCs becomes too complicated, perhaps a glowing sprite could be added to the mecha-headcrab model that would show whether the headcrab is hostile towards Combine or not. Potentially mecha-headcrabs could even be ‘hacked’ like turrets, so that mecha-zombies and mecha-headcrabs with green indicators are friendly towards the player, citizens, and vortigaunts. Because both headcrabs and zombies rely on surprise, this sprite should only be visible while the NPCs are advancing on an enemy and have been spotted.

    Benefits to the player

    An element should be added that the player can use to subvert the mecha-zombie and mecha-headcrab enemies. Either a ‘Combine control tower’, a generator that creates an EMP when destroyed, or some new EMP based weapon the player can use. For the sake of example, let’s say it’s a signal tower that creates an EMP when destroyed. Mecha-zombies and mecha-headcrabs caught in the EMP should revert to their original behavior. After all, they are merely regular headcrabs being controlled by Combine prosthetics. Once free of the Combine they will attack both Combine forces and the player. The player can use this to their advantage by thinning out heavily armed Combine positions. Whenever the player sees a signal tower, they will know they can use it to create an EMP that will turn the Combine in the area against one another.

    Another beneficial element of the mecha-zombie is that they could carry supplies for the player, especially in areas that would normally be scarce on ammo. The mecha-zombies can also carry items not normally associated with the Combine, like crossbow bolts or revolver rounds.


    In terms of appearance, it was mentioned in the post that mecha-zombies should be former rebels. This makes sense in the story because the mecha-headcrabs will primarily be used against rebels. However, I think it’s important to visually highlight that mecha-zombies are a Combine unit. I think it’s possible to make something appear visually more Combine or Rebel from a distance while leaving the up-close details to tell the story of exactly what the NPC is: for example, rebels are actually using civil protection gear (this can be seen up close) but because of the shape and color pallette they don’t appear to be Combine. Likewise, the mecha-zombie should use a darker color pallete to appear visually consistent with the Combine soldiers. However, upon closer inspection they are actually former rebel soldiers with a darker uniform. I think the blood / mutations on the mecha-zombie should be minimized to focus on their role as a Combine drone rather than a horror themed monster.

    Canister Reinforcements Ability

    I can’t personally take credit for this idea, as it was inspired by an earlier idea post by XBLAH. The most powerful ability of the mecha-zombie is that it can call headcrab cannisters for reinforcements. When the mecha-zombie sustains damage, it will emit a loud cry, followed by a short beep every second. There should be a sprite that flashes on and off on the mecha-headcrab indicating that the mecha-zombie is calling reinforcements. After five beeps, a headcrab cannister is called to the mecha-zombie’s location, killing it in the process. This will spawn several new mecha-headcrabs. The number should be configurable by the mapper. There should also be a configuration to set this ability to always trigger, never trigger, or only trigger when the mecha-zombie is below sky.


    The design of the mecha-zombie NPC should focus on two key goals: providing an NPC to synergize with existing Combine units, and giving as many tools as possible for mappers to craft interesting new scenarios.

    – Uses Combine squad slots
    – Breaks line of site between players and advancing Combine soldiers
    – Is friendly towards standard headcrabs in the absence of Combine forces
    – Can be turned against the Combine by EMP
    – Carries pickup items
    – Appears to be a rebel soldier in a darker color scheme that visually coheres with the Combine soldiers
    – Can call mecha-headcrab cannister to position

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