We have seen the new designs of Terran hero Raynor and Protoss hero Zeratul in a video which introduces the new Starcraft 2 universe.At the last of the video Zeratul said the Xel’Naga returned to make the end.This dramatic words are gives us some idea about the purpose of Xel’Naga.But here is the question why these creators want to eridicate these races.The answer is releated with the ancient Protoss.At these ancient ages before the Aeon of Strife some Protoss Tribes was controled by their own prides which lead them through to awful actions like murdering their own creators.So that made the Aeon of Strife which is a very heavy battle at Aiur. The planet and creatures in it will never forget that war.So the surrender Xel’Naga forces left the planet and at that time the seeds of hate can be settled down the minds of the Xel’Naga.We shall see the these seeds dessert  in Starcraft 2.