Kalathi

The Kalathi are a sentient alien race that was encountered by the Protoss a few centuries before StarCraft.

The Kalathi became embroiled in a civil war, which the Protoss interfered in. This resulted in the Kalath Intercession, in which the Protoss deployed Colossus robots against the Kalathi, who were virtually decimated by the attacks.

The Protoss have since avoided entangling themselves in the affairs of other intelligent species.

{ref}}
 * 2007-10-08. SC:L Metzen Interview - Lore Exclusive. StarCraft Legacy. Accessed 2007-10-08.
 * 2007-06-28. Colossus. StarCraft II Features at Blizzard Entertainment. Accessed 2007-07-01.