Xel'Naga
The Xel'Naga (whose name, according to the original StarCraft manual means "Wanderers from Afar") are an ancient race that has to date only been featured in the lore of the StarCraft series; their only appearances have been in the form of relics. The Xel'Naga play important roles in the backstories to both the Protoss and Zerg, being responsible for manipulating the evolution of the two races, along with an unknown number of other species. It was speculated that a player could control the Xel'Naga in StarCraft II and although this has been firmly denied by Blizzard Entertainment, they have confirmed the Xel'Naga will contribute to the game's storyline "in a rather epic tale".
Read more about this topic: Races Of Star Craft