Hydralisk

The Hydralisk, which derives its name from its serpentine body (a blend of hydra and basilisk), is a Zerg breed. They are a modified form of the Slothien, a genus assimilated into the Zerg Swarm, and are approximately 18 feet long; when "standing" they can reach over eight feet in height. They can move faster than a Terran.

In StarCraft's cinematics, the Hydralisk uses its scythe-like front arms to attack and assist movement, but they are rather vestigial in actual gameplay. In-game, the hydralisk is a ranged ground soldier of the Zerg race, attacking with projectile needle spines fired from underneath its head plates, capable of piercing ten centimeters of neosteel. According to StarCraft: Revelations these spines are slightly poisonous. With a Hydralisk Den and prerequisite Spawning Pool, it is produceable in any Zerg Hatchery structure. As with most Zerg units, the Hydralisk is most effective en masse.

Strategies
Hydralisks have a high rate-of-fire and deal explosive damage, making them more effective against large units such as Protoss Dragoons. They are capable of striking airborne units.

Producing Hydralisks requires a Hydralisk Den, a structure that contains the Hydralisk strain for the Zerg race. Hydralisks are produced from Larvae, however, which are in turn produced by Hatcheries, Lairs and Hives.

The Hydralisk Den contains these upgrades - Grooved Spines (adds to Hydralisk spine range), Muscular Augments (adds to Hydralisk movement speed) and, in StarCraft: Brood War, Lurker Aspect (allows the Hydralisk to become a Lurker).

Employing Overlords to drop Hydralisks around an opponent's mineral gathering points will significantly delay him or her, especially in the early stages of game when minerals are most scarce and most necessary. Although such an attack requires effort and micromanagement at a time when base construction is crucial, the inflicted delay should provide adequate time to mount an assault before the target opponent can completely recover.

Counters
Effective against early-game Hydralisk rushes are Siege Tanks/Marines as the Terran, or Zealots/Dragoons as the Protoss. In early Zerg/Zerg games, Hydralisks are only stoppable with other, larger Hydralisk groups. Zerglings can also be effective, provided the battle takes place in an open area and the Zerglings can surround the Hydralisks. In longer Zerg/Zerg games, Zerglings with the Defiler's Dark Swarm ability are often an effective response, while Reavers are a powerful Protoss alternative. Units that inflict significant damage (such as Terran Siege Tanks or Protoss Reavers) are the most effective against Hydralisk attacks.

Hunter Killers
Hunter Killers are a special, more powerful Hydralisk variant. Compared to regular Hydralisks, they are tougher and deal more damage. They are occasionally available in the single-player missions.

Originally created and used exclusively by Daggoth of the Tiamat Brood, they protected Infested Kerrigan after her rebirth. Daggoth sacrificed a number of Hunter Killers on the Amerigo to delay attacking Terrans.

During the Brood War, Daggoth was a rival to Kerrigan. However, Hunter Killers fell under Kerrigan's control on multiple occasions.

Lurkers
Lurkers are a breed of Zerg which can attack from underneath the ground.

By the time of the Brood War, the Zerg had bred the Lurker from the Hydralisk. The Lurker burrows into the ground and attacks enemies above with a wave of subterranean spikes. The spikes do normal splash damage and are particularly effective against infantry. Unlike other Zerg units, the Lurker can only attack while burrowed. Burrowing does not need to be researched for the Lurker to burrow. If the Lurker is above ground, they gain mobility, but become defenseless.

Warcraft III
A Hydralisk unit is available as an easter egg in the single player campaign of Warcraft III: Reign of Chaos. In the second night elves mission, "Daughters of the Moon", the Hydralisk is hidden in the forest north of the final undead camp. To get to it, use the ballistas to blast down the trees.

In WarCraft III, the Hydralisk's attack can clearly be seen - it opens shoulder plates to fire its spines at the enemy (as opposed to firing them from the groove in its lower jaw).