Xel'Naga

The Xel'Naga are an ancient species in the StarCraft setting, believed extinct, whose actions are tied to the development of both the Protoss and the Zerg; both races were genetically engineered by them. The Xel'Naga created the Overmind to unify the Zerg into a hive mind, and the Overmind later turned on and assimilated its makers. Their homeworld is Ulnar, which Kerrigan investigates in Legacy of the Void. Their artifacts recur throughout the series, including the device that de-infests Kerrigan, and the rogue Xel'Naga Amon is the final antagonist of StarCraft II; Kerrigan herself ascends to become a Xel'Naga to defeat him.