Many aliens were harmed during the production of this guide
No Marines were harmed during the collection of data for this guide.
This guide is now obsolete with the release of Swarmopedia. All information can be found there, although you can still look around here and get some ideas on what you'll be facing.

The basic alien that you will fight throughout all the campaigns. Drones "swarm" you with insurmountable odds. These enemies, however, are very easy to defeat by shooting and punching. It is not recommended to go into close quarter combat because their claws can shred through marine armor with ease. Flame and Tesla damage type weapons stun them allowing for easy run around and/or elimination. Drones will also leap to cover large amounts of space and easily intercepts the squad. Drones include a variety of different sub-types such as:
Parasite Drone: A drone with a parasite on its back. Once killed the parasite jumps off of it.
Uber Drone: A larger drone that supports quite a bit of health but it is slow and fat.
Orb Drone: A drone that, once killed, launches several orbs that act like the boomer's.

This bug launches multiple (three) acid projectiles towards the marines, dealing horrific damage if they impact. One ranger is no problem, easily avoidable when rolling around but the real issue comes when they have a numbers advantage making it difficult to move without getting hit. They can usually take one or two more hits than drones but still aren't very hearty. Fire stops them for a couple of seconds but they will continue firing after that.

Buzzers have little health and, when they make contact to marine armour, deal little damage even on higher difficulties. Their real potential comes from when they actually do hit you: shaking your screen about, blurring your vision, and making you angry. Buzzers not only are annoying when making contact with you but also when they are flying around and set on fire: they emit a loud and aggravating screech that is unbearable to headphone users. They fly at fast speeds and have a small hitbox making them difficult to hit with anything other than flames, teslas, explosives, and auto-aim weapons. they can be slowed by freeze and tesla but do not slow down due to fire.

The Boomers are large aliens that are not a threat at first sight, dealing little melee damage to marines and moving slowly. However this disappears within the first couple of seconds considering they swell up and once you shoot them enough they'll pop, throwing out small egg like spheres that take a while before finally exploding dealing tremendous amounts of damage to marines especially if hit by multiple bombs. Boomers will explode on their own if left alive whilst bloated so conserve ammo if needed.

A large alien that uses its four front legs as a huge shield to negate all incoming damage from its enemies. If a shieldbug happens to get close to a marine it will hit him/her to send them flying a good distance while also dealing a decent amount of damage. Its faults are noticable when marines flank around it to hit the fat weak spot behind the shield, making it not last very long. Any elemental damage will make it drop its shield for a second or two while also doing damage to it. Before it is engaged in combat you have a second window to hit it before its shield is put up. As of the release of RD the shieldbug also blocks all damage from piercing weapons like the rail rifle.

Although it isn't an enemy itself, it often times blocks player progress and is needed to be destroyed to complete the mission. The flamer and mining laser both destroys biomass quickly. Destroying it will call drones and rangers to that area so be prepared when it is burned down. Don't walk into the biomass either or it will deal minimal damage to marines.

Eggs do not deal damage by themselves (unless a marine comes in contact with it) but they do eject fresh parasites to latch onto a marines face! Eggs are fragile by shooting and burning (or even punching) but be sure to do it quickly or else a parasite will jump out of it. Burning eggs will pop out a parasite anyways but they do not latch onto your face because they are on fire as well.

Grubs are harmless, dealing absolutely no damage to the player. They pop out of small eggs (not to be mistaken for parasite eggs) and will swarm the marines to nibble on their feet. Do not fret, these annoying, yet not annoying, creatures can easily be removed by stepping on them. Don't waste ammunition on these. Tesla Cannons lock onto these so be careful not to waste ammunition when they are around.

The most harmful alien of them all. Despite its size, this little fella can latch onto your face and infest you. Punching or shooting them before they get on a player is ideal and is the only way to get rid of them before they get on a player's face. Medical supplies from medics or your health kit can help make you survive longer or completely remove the infestation. Infestation can also be removed by using electric armor, curing you immediately. If none of these options are available at the time of infestation (no medics are alive or no meds) then run off away from the team and let them finish their job so they don't latch onto another nearby marine, type in console "asw_suicide" for instant death, or let your teammates kill you to prevent all parasites from ejecting.These are bright and have predictable spawns so watch out for them. Medics keep on your toes I don't want to lose any marines to infestation.

This big creature does nothing more than sit in one spot spitting large cabbages at the marines that open up and explode dealing massive amounts of damage. They do not have much health (correction, according to Alien Swarm Wikia they have the largest pool of health aside from the Queen...) however getting to them is a problem considering they usually have allies running about and their bombs restrict the squad's movement.

Harvesters are large egg sacks with legs. These creatures poop out alien "harvesites" that I will talk about later. Harvesters do not attack you directly and do their best at staying out of your way. They have a decent amount of health but when they die they launch several harvesites that fly toward you. Harvesters also do damage to marines if they decide to run into the harvesters and pet them much like Biomass.

Do NOT mistake these for parasites. These turd brown creatures are made from Harvesters and are kamikaze aliens, meaning they will launch themselves at you: killing themselves, but dealing damage to you. Although on normal this might not be an issue anything above that tends to get marines killed quickly with little to no warning.

This beastie was not in the official 2010 campaign but can be found in some of the newer campaigns. The Shaman heals its allies with a beam which is like the medic's medgun but much faster and has a seemingly endless supply. The creature is fast but supports little health. Its priority is to heal the most damaged ally before healing the rest but does not heal other shamans.

Somehow this monstrosity made its way from the Half Life 2 Universe to the facilities and sewers infested with Swarm that the marines must go through. Much like in Half Life 2, this large creature will rear its large head and make a loud sound (can't really think of a description right now :/) before it charges into a marine, sending him or her flying through the air much like the shieldbug does. It surprisingly isn't very hearty and doesn't do much damage on Hard difficulty and below but it could do a lot to hinder a marine when making contact with its head, often knocking players into a large pile of Drones, other hazardous objects, or just slowing down squad progression in general.

The queen in Alien Swarm looks awefully familiar to the one in the Aliens movies however that's not the point. The queen, like the shaman, was unused in the Official 2010 Alien Swarm Campaign and is used in one or two custom campaigns that I have found here and on ModDB. Unlike the Shaman, however, it is fully working with all animations in tact. The Queen is a serious threat and is not a push over, having 5 health bars and possessing the ability to erect claws out of the ground to hold marines in place. Not only holding them in place, but also dealing a good amount of damage to them as well. Apparently punching the tentacles will allow you to escape the tentaces instead of waiting for them to move. The Queen also has a ranged attack similar to the ranger, firing three projectiles.Nuke it from orbit, it's the only way to be sure.

------General Achievements (achievements obtained by said objective with any alien):-------

• On the Ready Line
  Kill 1,000 Swarm.
  
• Close Encounters
  Kill 20 Swarm with melee attacks in a single mission.
  
• Smoking Barrels
  Kill 5 Swarm with explosive barrels in a single mission
  
• Autogun Expert
  Kill 250 Swarm with an Autogun.
  
• Assault Specialist
  Kill 250 Swarm with the Assault Rifle.
  
• Pyrotechnician
  Kill 250 Swarm with a Flamethrower.
  
• Prototype Professional
  Kill 250 Swarm with a Prototype Rifle.
  
• Electro-Stunned
  Stun 6 Swarm with a single Stun Grenade.
  
• Blast Radius
  Kill 6 Swarm with a single Grenade.
  
• Vindicator Veteran
  Kill 250 Swarm with a Vindicator.
  
• Stay Frosty
  Freeze 6 Swarm with a single Freeze Grenade.
  
• Damage Amped
  Kill 15 Swarm with all four marines under the effects of a Damage Amp in a single mission.
  
• Small Arms Specialist
  Kill 250 Swarm with PDWs.
  
• Another Bughunt
  Kill 5,000 Swarm.
  
• Shotgun Specialist
  Kill 250 Swarm with a Shotgun.
  
• Static Defender
  Kill 500 Swarm with deployable Sentry Guns.
  
• Peace Medic
  Heal 300 points of damage in a single mission without dealing any non-melee damage to the Swarm.
  
• Hornet Barrage Expert
  Kill 100 Swarm with Hornet Barrages.
  
• Minigun Master
  Kill 250 Swarm with a Minigun.
  
• Pistols Expert
  Kill 250 Swarm with Twin Pistols.
  
• High Voltage Expert
  Kill 250 Swarm with a Tesla Cannon (Don't die of old age).
  
• Slaughter Soldier
  Kill 250 Swarm with a Chainsaw.
  
• Tactical Explosives Expert
  Kill 100 Swarm with Laser Tripmines.
  
• Firewall Specialist
  Kill 100 Swarm with Incendiary Mines.
  
• Railgun Specialist
  Kill 250 Swarm with a Rail Rifle.
  
• Professional Marksman
  Kill 250 Swarm with a Marksman Rifle.
  
• Grenadier Expert
  Kill 250 Swarm with a Grenade Launcher.
  
• Kill Them All
  Kill 25,000 Swarm.
  
• Nuke From Orbit
  Kill 100,000 Swarm.
  
• Combat Specialist
  Kill 250 Swarm with the Combat Rifle.
  
• Screamin' Eagle
  Kill 250 Swarm with the Desert Eagle.
  
• Devastated
  Kill 250 Swarm with the Devastator.

----------------------------Swarm Subtype Achievements: (Drones)-----------------------

• Clear Firing
  Kill 25 drones without friendly fire. Four marines must be present in the mission.
  ----------------------------Swarm Subtype Achievements: (Boomer)----------------------
  
• Quick and Dead
  Kill a Swarm Boomer before it inflates.
  ----------------------------Swarm Subtype Achievements: (ShieldBug)-------------------
  
• Shield Down
  Deliver the finishing blow to a Swarm Shieldbug.
  ----------------------------Swarm Subtype Achievements: (Eggs)-------------------------
  
• Scrambled Eggs
  Destroy all Swarm Eggs in a mission without allowing any to hatch.
  ----------------------------Swarm Subtype Achievements: (Ranger)----------------------
  
• Under the Gun
  Roll under a Swarm Ranger projectile.
  ----------------------------Swarm Subtype Achievements: (Parasites)--------------------
  
• Infestation Savior
  Cure an Infested marine.
  
• Parasite Puncher
  Kill a Swarm Parasite with a melee attack.
  ---------------------------Swarm Subtype Achievements: (Grubs)-------------------------
  
• Bug Stomper
  Kill 100 Swarm Grubs.

In-game Screenshots: Me and the Swarm
Visual Mod Used: No Grain Mod by Duke Duke'em https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=935378259&searchtext=no+grain
Game itself: Former Black Cat Games, Valve Corporation, and Reactive Drop Team

sv_cheats 1
firstperson
asw_controls 0
asw_hide_marine 1
asw_god 1
asw_ent_create asw_shaman
asw_marine_rolls 0
asw_laser_sight 0
asw_simple_hacking 1
asw_suicide
map (Jacob's Rest Campaign)
asw_draw_hud 0
asw_ent_create npc_antlionguard
ai_disable
asw_ent_create npc_zombie