Endless Days

For their arrogance, two brothers are cursed to walk the Earth forever, unable to have the death that would free them from their torment. One suffers intense pain in the presence of sunlight, the other intense pain in its absence. Thus, they decide that they must live apart, each thriving where the other fails. As they go their separate ways they take very different paths through history, resulting in an ending that pits brother against brother for the fate of the world.

The first fantasy book by Thegn.