Calus is a planet in the Koprulu sector.

The Terran Dominion established a security outpost in the cliffs above a valley. [1]

Plot branch : Sarah Kerrigan chooses to evolve the zergling

During the Second Great War, Abathur discovered that local karak had the ability to vault through the air to attack prey - a trait he wished to assimilate to the zergling strand. After acquiring the karak's essence, Abathur spun the new sequence into the zergling strand to create raptors that scaled the cliffs and destroyed the outpost.