Demon lore has gotten extremely messy with the whole Infinite thing, as well as how Demons only die when killed in the Nether has been handled. Has it been explained how Illidan was brought back given that he was killed in Outland which is currently located in the "Edge of the Nether"? Or has it been special pleading that the edge of the Nether functions differently to being deeper in the Nether or that Demons can additionally be revived through other means? Or simpler, did we just not kill him at the top of Black Temple? Haven't heard the answer to this.