Nameless One

The Nameless One was a nameless human with a unique form of immortality.

Rather than being protected from injury, he had regeneration abilities, like a troll. His specific brand of unending life also allowed him to automatically rise from the dead. However, with each rising, he lost large chunks of his memory, leaving him little clue as to what he was doing or even where he was.

To counter this disorientation, the Nameless One had important facts tattooed on his back in large runes. These became hard to read, however, as the other side-effect of this immortality was to always bear the scars of combat. In time, the Nameless One was heavily scarred, a testament to how many times he had "died."

Trivia
In the special version of Baldur's Gate II: Shadows of Amn, it is possible to buy items from a merchant in the city of Athkatla that mention the Nameless One.