Alien Grunt

The Alien Grunt (also known as Xen Grunt) is the primary combatant of the Nihilanth's Xen army.

Overview
Tough, strong, and extremely hostile, Alien Grunts stand about seven feet tall and are armed with a biological weapon called the Hivehand, which shoots biological "bullets" known as hornets. At melee range, it will also use weaponless hand-to-hand combat.

Alien Grunts share many features with their Vortigaunt counterparts: multiple red eyes, backwards-jointed legs, hoofed feet, and a short arm extending from their mid-torso, which is used for feeding.

Grunts are also equipped with metallic armour around the groin and shoulders, as well as metal helmets and shoes, though it has been speculated that this is actually a natural 'shell' formed as a result of a calcium-rich diet. Interestingly, this armor completely protects the Alien Grunt's back, but is open in the front leaving the Grunt's entire lower torso exposed. This may be to allow for the third arm, or indicate that vital organs are more vulnerable from behind.

Behavior and Skills
Alien Grunts use intelligent soldier-based combat tactics, such as running between cover nodes, while standing still to fire their hivehand weapon at enemies. They have roughly 75% more health compared to HECU Marines (varying somewhat depending on difficulty); combined with their bullet deflecting partial body armor, this gives them high durability. On Hard difficulty, Alien Grunts can take 4 close range shotgun blasts or up to two dozen rounds of MP5/M4 fire to kill. They also demonstrate superhuman strength in various scripted sequences seen throughout the game; such as punching a HECU Marine through a concrete wall, or quickly prying opening a large set of heavy blast doors. Alien Grunts can be found being transported through a factory on Xen, stored in pod-shaped containers. The implication is that the Alien Grunts are manufactured beings, which is supported by the heavy amount of biological technology and weaponry featured in Xen warfare.

Weaponry
Unlike Vortigaunts, they do not seem to share the race's myriad energy-based powers; hence the need for the hivehand weapon. The Hivehand, which shoots hornets (sometimes known as "thornets"), seems to have an infinite amount of ammunition, which is constantly refreshed. The hornets seek out living things and attack them, making the attack useful for attacking from around corners.

Alien Grunts can also use melee attacks when at close enough range. They will primarily use their hands and arms to punch an enemy, dealing more damage than the longer range Hivehand attack.

Trivia

 * If the player does not accept the G-Man's offer at the end of Half-Life, he will put him (unarmed) into a large room full of Alien Grunts.
 * At one point in the game, a group of alien grunts appear to be commandeering, or at least have set up, an alien energy cannon, implying the necessary requirement of external weaponry.
 * In the original Half-Life, Alien Grunts take significantly reduced damage (roughly 50% to 60% of normal) if shot in the armor instead of in their exposed body with a Colt Python or Black Mesa Crossbow. Lower impact rounds, such as pistol/assault rifle bullets, buckshot, and even the primary fire of the tau cannon will outright ricochet off the armor without doing any damage at all. This is not true in Half-Life: Source, since the Source engine does not support different damage values/effects for different materials.
 * What the Alien Grunt's armor does is subtract 20 points of damage from any attack that hits it. Any projectile that hits the armor and does 20 points of damage or less will simply ricochet off harmlessly.

Behind the scenes

 * The original Alien Grunt model had a more bluish armor, slightly different skin textures, and the Hivehand apparently "built-in" in its right hand, although it was probably temporary. This model was kept in the retail Half-Life as a sprite for the Alien Grunts from the back rows in the 'bad' ending.
 * Before the Hivehand, the Alien Grunt was originally to use a weapon dubbed as a "Black Hole Gun".
 * Originally Alien Grunts were to be able to be gibbed in Half-Life: Source. The gib textures have higher resolution than the grunt's textures.

List of appearances

 * Half-Life
 * Half-Life: Opposing Force
 * Half-Life: Blue Shift
 * Half-Life: Decay
 * Half-Life 2: Raising the Bar