So whats the history on Khaine? I know he got his butt kicked by Slaanesh and was split up into shards, and these are the avatars. But what about with Vaul and way back when, like Eldar mythology? In other words... Who, what, why and how(As in came to be, exist) is Khaine?

Oh, and if Dark Eldar are anything like Dark Elves, wouldn't Dark Eldar worship Khaine?