Half-Life/Enemies

There are a wide variety of enemies you will face in the game, both alien and human. This is a comprehensive list of all the enemies featured in the game as well as their health, damage infliction, and a description. The damage and health are given in the form of three sets of numbers. This is to show the value at the three difficulties. For example, the headcrab's attack is given as 10/10/20. This means that at on easy and medium difficulty, a headcrab attack does 10 damage, while it does 20 on hard difficulty.

Early Game Enemies

Barnacle

• Health: 10/10/10
  
• Damage: Instant death if manages to get you pull you up to the top.

Barnacles are stationary aliens that attach to ceilings. They have extremely long and sticky tongues that they hang down from the ceiling. These can be hard to see, especially if the barnacle is stationed up on a high ceiling. If something wanders under the barnacle and touched its tongue, the barnacle will immediately begin reeling it in. If you wander into a barnacle's tongue, the same will happen to you. If you do not kill the barnacle by the time you are sucked into its jaws, you will be instantly killed. Thankfully, however, it only takes one swipe of the crowbar to kill a barnacle, so if you do get caught by one, simply swipe the barnacle when you reach its mouth. This will not save you from falling damage, however. Barnacles will not distinguish between you and an enemy, and can be used as traps to snag marines. The pistol or crowbar are recommended for taking out barnacle- anything more powerful is a waste of ammo.

Headcrab

• Health: 10/10/20
  
• Damage: Jump Attack 10/10/20

Headcrabs are the first enemy encountered in the game. They're rather weak, but can be dangerous in groups. Headcrabs are usually found hiding in damp or dark areas, waiting for prey to ambush. When attacking, they launch themselves at their intended victim's head, making a screeching sound. If they successfully attach to an NPC's head, they will dig into its brain and turn it into a zombie (see below). Headcrabs are best taken out at a distance with the pistol or, later in the game, the hivehand from a distance. If you are good at dodging their jump attacks or are encountering them in close quarters, you may also choose run up and hit them with the crowbar.

Mawmen

• Health: 50/50/100
  
• Damage:
  Single Swing 10/20/20
  Double Swing 25/40/40

Mawmen, or zombies, are humans that have fallen victim to headcrabs (see above). The infestation has mutated their hands into long, sharp claws, and there is a giant gaping hole in their torsos. Mawmen are usually found standing around or feeding on corpses, but are sometimes found on the floor, feigning death until they are shot or someone approaches. They only have one form of melee attack and no form of long distance attack. Mawmen are rather slow and can easily be taken out with a crowbar if you step back after each few crowbar swings to avoid the zombie's pathetically slow claw swipes. Alternatively, you can use the pistol at long range or if you need to take them out quickly.

Alien Slave

• Health: 30/30/60
  
• Damage:
  Side Swipe: 8/10/10
  Overhead Swipe: 25/25/25
  Electricity: 10/10/15

Alien Slaves, also referred to as vortigaunts, are slaves from the alien planet Xen ordered by their master (whoever that may be) to kill anything that isn't from Xen, specifically humans. At long range, they attack by an electrical charge. When met at close range, they attack with their claws, causing a more damage than their electric bolt. You will know when a vortigaunt is about to attack because they will charge up their bolt for a couple of seconds, emitting green electricity into the air. When this happens, it is best to find cover because, even if you are moving, a vortigaunt's electric attack hardly ever misses a target in its range. Vortigaunts are best taken on with the shotgun at close range or with the [[Half-Life/Weapons#9mm Pistol|pistol at longer ranges.

Houndeye

• Health: 20/20/30
  
• Damage: Wave Attack 10/15/15

Houndeyes are small, yellow and green striped dog-like creatures that balance on three legs. When one is in range of a target, it will charge up an attack, making a distinctive whine before unleashing a wave of energy. A houndeye's attack isn't terribly damaging, especially for the amount of time it takes to prepare, but when several attack at the same time, the waves enhance each other, creating a stronger, more damaging wave of energy. When facing a pack of Houndeyes, the best strategy is to find a bottleneck or corner where they must come at you one at a time. Recommended weapons for dealing with Houndeyes are the crowbar if there is only one or two of them, and the shotgun or pistol when dealing with a pack.

Bullsquid

• Health: 40/40/120
  
• Damage:
  Acid Spit 10/15/15
  Tail Whip 25/35/35
  Head Butt 15/25/25

Bullsquid are violent Xen creatures that are hostile to all creatures, aside from other bullsquid. At long range, it will spit acid with decent accuracy, but slow enough that it can be easily avoided. At close range, it is more dangerous, attacking by either slashing you with its tail or knocking you across the room. If there are other enemies around, like headcrabs or marines, they will often attack these enemies before attacking you. You can use this to your advantage to inflict damage to it while it is not focused on you. At long ranges, a bullsquid doesn't present much of a threat as long as you dodge its slow moving projectile spit, so the pistol should be all that is required. At close range, however, the bullsquid is much more dangerous, and may require a few shots from the shotgun or magnum.

Human Grunt

Also known as grunts, marines, or simply the military, the HECU are a special military task force dispatched by the U.S. Government to contain the incident at Black Mesa by killing everything, including the facility personnel. HECU soldiers are the most common human enemy, and utilise a variety of weapons, vehicles and tactics against you. Grunts are usually armed with an MP5 submachine gun and hand grenades, and will utilize squad tactics to surround and destroy you. In many instances, the soldiers also make use of vehicles, such as tanks and attack helicopters, and fixed weapons and fortifications, such as mounted .50 caliber machine guns and artillery pieces.

Assassins

Commonly known as Black Ops, Assassins are elite female operatives skillful in stealth and close combat, and utilize silenced pistols, grenades and (when up close) a variety of martial arts kicks and jabs. They have been confirmed to work independently of the HECU and apparently have their own objectives to complete, one of which is eliminating you. Black Ops are extremely fast and agile and can leap considerable distances, making them very hard to target. Often the only valid tactic is to back into a corner so they can only come at you from two directions which you can more easily monitor. If you have any, snarks are extremely effective against assassins, even if they don't kill them outright. When an assassin encounters snarks they will usually ignore you to fire wildly at the creatures, giving you a clear shot.

Gargantua

The Gargantua (or Garg as they are commonly referred) is a large blue armored creature. The Garg is one of the games most powerful creatures but very rare. The Garg attacks by shooting jets of flame from its hands and causing a shockwave of energy that goes through all obstacles. The Garg's armor is immune to normal munitons and is only vulnerable to Explosive, Electrical, Energy, and Acidic attacks. Unlike most other alien creatures the Gargantua is a valid target for Snarks. While the snark's biting is shrugged off, the acid released by a dying snark is effective so a large amount of snarks can kill the mighty Garg. The RPG, Grenades, Satchlal, Grenade Launcher, Gauss Gun, and Gluon Gun also do damige. The first Garg you encounter can also be tricked into an electrical arc, killing it. Gargantuas explode when killed, so keep your distance.

Gonarch

A giant beast that looks similar to a spider, Gonarch is a four legged creature with a large sack (similar to an abdomen) that hangs down below where its legs meet. As the second to last boss, Gonarch can only be found once during the game and it takes a large amount of damage to kill. The sack is Gonarch's weak point, and it can only be harmed when Gonarch isn't in "cinematic mode" - in which the beast progresses farther into its lair between battles.

Nihilanth

The boss of the game.