No one really knows where the Promethean Emperor came from.
Some say he was sent as divine punishment to the Titanic Hegemony for its overweening hubris. Some say has was the abandoned son of Kronos Deverin and sought the overthrow of the Hegemony out of a desire for revenge. Some say he was a slave that rose up to slay his masters. But really it does not matter from whence the Promethean Emperor came, only that he did.
The Promethean Flame