Nathan K -- he can hold two souls in his body. If he dies, he loses one yet lives on with the other. As long as he replenishes his second soul, he cannot be killed. Nathan K is immortal.

BREAKOUT

After a year keeping a low profile in England, Nathan is eager to end his wait on Eternity, eager for Robin to return to hacking for him, eager for a fight. But he should be careful what he wishes for. When he learns of an Immortal being held prisoner in a converted castle, he helps a ragtag group led by an ex-Eternity agent to stage a jailbreak and ends up with a fight greater than anything he could imagine.

Because in the world of Immortals, rarely is anything what it seems. Especially when Nathan learns that the Cardinal is involved.