How bout something along the lines of a someone who was deeply religious. But somehow their faith was shattered and betrayed by the gods. So now they use the swords to capture souls and prevent the gods from getting them. Come to think of it though I have no idea if the people of Cyrodil believe in the idea of a heaven.
Yes, its called http://www.uesp.net/wiki/Lore:Aetherius
Hell is called http://www.uesp.net/wiki/Lore:Oblivion