The Transcendent One's identity is not known for certain until the very end of the game, although someone has left behind a trail of missing documents and much subterfuge in the service of covering up the existence of some adversary, along with all evidence of The Nameless One's past. A similar trail of Deaders, such as the fathers of Finam the Linguist and Hamrys, and Ravel herself, attest to the ruthlessness of this killer unknown.
The Transcendent One is the The Nameless One's mortality in a corporeal form, separated from The Nameless One by his request. Only Ravel's power was sufficient to enact the ritual which cursed The Nameless One with immortality.
He believes that nothing can change the nature of a man.
The mortality manifested into physical being and evolved, growing in power and intellect. He and The Nameless One (TNO) share a bond, and if either of them dies permanently, so shall the other. Unlike TNO, the Transcendent One remembers the past lives that both shared - and retains all of the powers and skills gleaned from them.
He later reveals that he sends out shadows after TNO not to kill him, but rather to make him forget through his death, and therefore leave the Fortress of Regrets (and Transcendent One himself) in peace once and for all.
- ↑ http://www.pathofexile.com/forum/view-thread/26950/page/4 path of exile