From SC2Pod
The enormous Ultralisk is the crown of Zerg evolution. With 400 HP and 20 base damage, the amount of punishment an Ultralisk can take is almost unreal. In groups these gargantuan monsters can tear down even the most stalwart defenses of any race.
Lore
Bearing little resemblance to the docile Brontolith that they were evolved from, the dreaded Ultralisk is a 20 meter long and 5 meter high living battering ram, the most powerful of the Zerg ground forces. They serve as the backbone of the Swarm’s armies and should be considered as dangerous as any armored vehicle. Ultralisks attack using large, bone-like scythes which protrude from their backs. Known as "kaiser blades", these scythes are nearly indestructible. Possessing monomolecular edges, these scythes are able to tear through most substances with ease. The best way to approach these creatures is from the air.
Weapons
Upgrades
StarCraft 2
The Ultralisk's StarCraft 2 model
The Ultralisk is back and stronger than ever in StarCraft 2. While it has lost its movement speed and armor upgrades, it has gained 200 additional HP, the ability to burrow, splash damage, and a powerful anti-building attack.