Characters & Enemies of Half-Life

Black Mesa Personnel
These are Gordon's fellow employees who are also caught up in the chaos caused by the resonance cascade. They're both under attack from the Alien Invasion and the Military Cleanup mission, and will aid Gordon as they can.


 * Scientists - Scientists aren't the bravest of the bunch, and they're definately not reliable in comabt, but they're willing to aid Gordon in whatever way they can; whether it's through imparting information, opening a door locked by a retinal-scanner or giving Gordon a shot to help take restore some of his health.


 * Security Guards - The security guards of Black Mesa are more than willing to lend a hand in killing the various menaces to the research facility. They act as secondary combat allies, helping you fight off enemies. Armed with a 9mm Glock, they are deadly accurate for security guards. Must be all that free time on the firing range...

Gordon can have two allies at one time, meaning you can have two scientists, two security guards, or one of each.

Military
Under direct orders to silence the facility by way of killing or capturing any non-Military personnel, the Military is ruthless in its execution. The chain of command keeps even the few Grunts who have second thoughts about the mission to kill civilians from doing anything about it.


 * Soldiers - The main bulk of the military forces, comprised of members of the US Marine Corp, identified as the HECU combat division in later installments; they are highly capable soldiers, able to work as a team and employ advanced tactics. The average Grunt is equipped with a MP5, with balaclava troops carrying shotguns, but both carry grenades.


 * Female Assassins - It's not entirely clear who they're working for, but the deadly assassins are equipped with silenced 9mm Glocks, grenades, and are capable of incredible acrobatic feats. They're encountered only twice throughout the entire game, but that doesn't mean that they aren't memorable, and they certainly are easy targets.

Vehicles

 * AH-64 Apache - The Apache is a strategic combat helicopter, equipped with a machine gun turret, and rockets. A single Apache is encountered in the game, acting as an unbeatable opponent forcing you to take precaution while advancing through areas. Capable of high damage and deadly accuracy, the Apache is very formidable, but is easily taken down with explosive arms or high-powered energy weapons. Upon finding the Rocket launcher, the Apache flies in for a close up attack, allowing you to shoot it down, leading to a climatic crash at the edge of a tall cliff.


 * V-22 Osprey - Having no weaponry of its own, the Osprey instead carries troops into battle, acting as a flying "soldier factory. Typically, it will hover over a battlefield as soldiers rappel down to the ground, dropping two at a time. When an Osprey drops troops, it will not drop more until you kill of it's previous soldiers, so you can't be overrun by an endless army of soldiers. But the Osprey will never run out of soldiers, leaving you either the option of working around it and it's troops, or shooting it down, which requires you to inflict equal damage on both of it's propellers, which can be difficult when it's moving.


 * M1A1 Abrams -The main battle tank of the military, it acts as one of the most deadly and difficult to traverse enemies in the game. The Abrams acts as an environmental enemy, as it doesn't move, and it's main priority is to keep the player ducking low, and moving carefully. The Abrams can be killed, but it has plenty of health, and getting a clear shot would put you in immediate risk of being killed by it. The only way to get a good shot would be to get behind, where it can't shoot you, but then you wouldn't have to worry about killing it, so it would be pointless. On an entertaining note, the tank can be killed by any weapon, even the crowbar, but it explodes on death, so doing this would cause you damage.


 * M2A3 Bradley -A secondary armored vehicle encountered in the game, the Bradley acts similarly to the Abrams, as it stands still and acts strictly as an environmental enemy, but instead fires rockets, and at a much faster rate than the Abrams. It also has the irritating benefit of being able to fire at 360 degrees, unlike the Abram, which had a massive blind spot behind it.


 * F-16 Fighting Falcon -A strategic bombing fighter jet aircraft, the Falcon also acts as a strictly environmental enemy. The Falcon cannot be destroyed by any means, even if it could it would be too fast to hit. The Falcon's only ability is dropping bombs in quick bursts as it flies by, for the most part however this is only used for cinematic purposes, and usually doesn't pose any real threat to the player.

Alien Fauna
The animalistic wildlife of Xen. It's unknown whether or not they are just the native fauna of Xen, or if they are utilized by the Alien Invaders as an attack force.


 * Headcrabs - Small parasitic aliens who launch themselves onto their prey, and attach themselves to their heads and take control of their cerebral, mutating them into zombie-like creatures, known as Mawmen. Headcrabs seem to prefer dark, tunnel-like areas and are often found in air ducts. They are also known to burrow into the ground while they wait for prey. All headcrabs are the offspring off a much larger and mature headcrab, known as a Gonarch (nicknamed Big Momma).


 * Mawmen (Zombies) - A Mawman is the gruesome result of a Headcrab's coupling with a human host. The Headcrab mutates the host, causing it to grow deadly bone-like claws where it's hands used to be, and to develop a giant, vertical mouth on its chest, giving the Mawman its moniker. It's rumored that even larger and more mutated zombies lurk in the darker parts of Black Mesa.


 * The Gonarch (Big Momma) - An elephant-sized creature vaguely resembling a Headcrab, is the final part of the strange lifecycle of the small parasite. The Gonarch is essentially armor plated, except for the large egg sac that dangles beneath its body where it rapidly produces tiny infant Headcrabs. The Gonarch is red with four large sharp legs, giving it great mobility, which it quickly exploits with a series of charging attacks and stomping on you. Additionally, the Gonarch can launch a large glob of biotoxins at its foe, making it a difficult foe to fight. Only one is encountered in the game as a boss, the battle that takes place upon encountering is so great, it takes place in it's very own chapter, known simply as "Gonarch's Lair".


 * Barnacle - Seemingly a long-lost cousin of the sea barnacle, this red lump of a creature hangs from the ceiling, where it dangles a long, sticky green tongue down to the floor, waiting for prey to walk into it. Once caught, it will draw its prey up into its mouth to eat, with it's two sets of mouths. The barnacle acts as an environmental enemy, almost like a "ceiling land mine" if a barnacle pulls you all the way to it's mouth, it will kill you in one bite, so "look out for tongues!"


 * Houndeye - A small, green, three legged dog-like creature with one large, multifaceted eye; it travels in packs and can generate a powerful burst of sonic energy, that can deafen and disable potential attackers and prey. The hound eye is a fast and common enemy, but has little health, making it rather threatening, but be careful, their sonic blast blaring in your ear buds is deadly in it's own sense.


 * Bullsquid - The natural predator of the Headcrab, and anything else it can find. The Bullsquid is a highly aggressive life form about the size of a lawnmower, and twice as likely to tear you apart. The Bullsquid is bipedal, that it walks on two legs, with tentacles surrounding its mouth. Due to it's aggression, it will attack its own kind just as readily as a Headcrab or human. It will bite, ram, lash with its tail, and even spit a glob of acidic saliva at its target with deadly accuracy.


 * Leeches - Small, white worm-like aliens that dwell in water, are found in certain areas of the game. Not capable of doing much damage alone, they're encountered in large groups and can do sufficient damage if you don't keep up the page.


 * Ichthyosaur - Said to have been hauled from the Challenger Deep, and supposedly from the Triassic period, the Ichthyosaur is a large sea predator whose true origins are much, much farther away. Capable of swimming at high speed to chase down its prey, the Ichthyosaur is a deadly predator and extreme caution should be taken when one is suspected to be in the water. The Ichthyosaur is encountered throughout the game in large bodies of water, and acts similar to a mini boss, as it isn't encountered common enough to be a basic enemy, and is usually found in an area that requires you to kill it in order to progress ahead.


 * Snarks - Small creatures that nest in tight spaces, these enemies also act as living weapons that scramble around until they find any life-form they can attack, including you, at which point they will go berserk and pursue that target, attacking viciously until they self-destruct fifteen seconds later. Snarks can be found as ammo in small organic nests, which are hard to find, making them a special weapon meant to be reserved for special purposes.


 * Tentacle - The Tentacle is a long, green, plant-like creature encountered in various locations throughout the game. Tentacles are blind, leaving it to hunt by sound, making silence important for sneaking past it unharmed. When it finds its prey, it uses the heavy armor plating at the end of its beak to crush or skewer it, and then drag the mashed creature to the ground beneath it. Tentacles are environmental enemies, and cannot be killed, damaging them will cause them to retreat back into their burrows, but they will resurface seconds later. Tentacles can be encountered either alone, or in groups of two or three.


 * Gargantua - The Gargantua is an large, hulking blue armored alien beast with a single small eye, with two tree-sized arms, and two vestigial arms, used to pick up and devour it's deceased prey. Its armor has the ability to resist most conventional forms of damage, and its physiology makes it capable of performing incredible feats of strength. It's primary arms end in heavily armored beaks, which have been shown to crush soldiers into red paste, can split open to reveal organic flamethrowers. And by stamping its foot, it can generate a streak of energy that races toward it's target. The Gargantuan is by all means a boss enemy, and often requires extraordinary means to defeat, whether it being a massive surge of electricity, or a military artillery strike. However the Gargantua can also be defeated by using basic heavy weaponry, such as Rocket's, explosives, and energy weapons.

Alien invaders
Sapient, three armed aliens who inhabit the Borderworld of Xen. They utilize organic technology and are apparently telepathic. There's also reason to believe that they are enslaved.


 * Vortigaunt (Alien Slave) - A humanoid green alien with one large red eye surrounded by several smaller eyes. The Vortigaunt is capable of generating a bolt of green electricity, and is able to use its natural claws to attack its target. The Alien Slave wears collars and shackles as part of their bondage.
 * Alien Grunt - Large, powerful humanoid who grows thick, metallic body armor and wields an alien Hivehand as its primary weapon. It is also strong enough to beat its opponent senseless, having been witnessed throwing a human through a concrete wall. They are either mass-produced, or packaged in factories on Xen.
 * Xen Masters (Alien Controllers) - Small and weak aliens with impressive psionic powers. Capable of flight and generating balls of energy, some of which home in on their target. Its large, flower-like head contains a strange, pyramid-like structure of unknown purpose.
 * The Nihilanth - The immense being capable of holding open the rift to Earth, and who gains his power from the crystalline structures found in Xen, which adorn its chamber, and is even contained in its flower-like head - similar to the Xen Masters. The Nihilanth bears a resemblance to the Xen Masters and a Human Fetus and features cybernetic augmentation and marks of surgical alteration, which seem incongruent to the organic technology of the Xen aliens.


 * Manta Flyer - A large flying creature that bears a resemblance to Manta Rays on Earth. Instead of being harmless tourist attractions, however, the Manta Flyer is capable of generating a deadly beam of energy that can take down an Osprey transport. Additionally, Manta Flyers can be used as teleport destinations, allow them to drop troops into battle.