Intercession

After living for centuries, Rob is tracked down to Portland, Oregon by another immortal. Together, they compare their (usually violent) back-stories, spanning from the Crusades, through World War I and II, into the present day. They do their best to apply some scientific method to exploring the boundaries of their unique ways of avoiding death. To their surprise, they discover they have a common origin, and that it's up to them to stop a lunatic from destroying the planet. Along with the supernatural abilities, adventure, fighting, self-discovery, and sprawling history, there's a sprinkling of Lovecraftian cosmic horror.