I finally figured out who the Nameless One from Planescape: Torment really is. Now, this may sound barmy at first, but it really does make sense. You see, the Nameless One is actually...
Tom Marvolo Riddle.
Yes, that's right. The Nameless One was once Voldemort, aka He-Who-Must-Not-Be-Named. How is this possible? Well, here's what I think:
In an alternate (fanfiction) version of the Harry Potter universe, the Earth is invaded by the githyanki armies, aided by rust dragons from Acheron and devil-worshipping clerics. It is the latter that truly shakes Voldemort's worldview. They have magic he does not understand, and, what's more, they can teach it to Muggle cultists. In fact, they don't even care about the wizarding world at all, since there are far more Muggle souls to corrupt -- and their hunger for magic makes it very easy to corrupt them.
At last, Voldemort actually gets a look at Hell, and he finally understands what Dumbledore meant when he said there were much worse things than death. He repents his evil deeds, and in so doing, reverses the damage to his soul caused by his Horcruxes. So much damage was done that the repentance caused horrible pain beyond imagining, but more terrifying than that was the realization that it was not enough. Voldemort had done so much evil that he could no longer make up for it in a mortal lifetime.
Now, Tom Riddle found himself in a truly ironic state. He had long sought immortality, but it was that which brought him to destruction. He was free of the old immortality, but to avoid being damned, he had no choice but to seek a new one. And, thus, He-Who-Must-Not-Be-Named became the Nameless One. He got the immortality he wanted, but for a far different reason — because regret had truly changed the nature of a man.
Ah, but you say the timeline doesn't match up? Surely the lich queen of the githyanki wasn't around when the Nameless One first became nameless? Well, when Voldemort finally breached the barriers separating Earth from the planes, he inadvertently managed to send himself far back in time — much like a certain other Planescape character in the Faction War. :mrgreen:
Here's my choices for him.
1. Cain
2. The human who started the Blood War.
3. Kas the General of Vecna
4. Longinus.
5. Frankenstein