Enderstar is a villainous enderman sorcerer. When he was a child, he got bullied for being 'different'. When he grew up, he began to speak of great plans and this got him exiled from The End.
He then went to the Nether and gathered a great army of local mobs to invade the Overworld. Their first attempt was a failure, forcing Enderstar to hole up in a nether fortress and focus his attention to the Nether.
Both EnderStar and Herobrine want to destroy Villagetown and all their attempts has failed so far. It is likely they will begin to work together, with Enderstar under Herobrine.It revealed that his true name is Nova in NK6, and when they used the tellstone in NK6 it seemed that EnderStar was a very powerful wizard.