From SC2Pod
The Brutalisk is a Zerg "boss" unit that will only appear in the single-player campaign and map editor. Not much is known about it at the moment, but it is described as "a large, Queen-like unit that resembles a cross between a Zergling and Hydralisk". Its first appearance is during a mission where the player must gather minerals from a map that has its lower levels flooded with lava at regular intervals. If the Brutalisk is caught in the lava surge, it is killed instantly. Currently, there is a Research Achievement in the game that requires you to kill two Brutalisks to unlock additional damage for all vehicles.
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