Xel'naga

Xel'nagas are a psionically-attuned, ancient, cosmic race. They were occasionally referred to as one of the most powerful species known in the world. While there are vague references of the Xel'naga conquering territories and uplifting species, their most notable involvement was with the Protoss and Zerg. Their interest in these two species was due to the Xel'naga's cyclical life cycle. When the incredibly long-lived Xel'naga were due to come to an end, the xel'naga would use these two species to be reborn.