Entire pantheons of gods and goddesses, Valkyries, immortals from fiction (Lovecraftian, for example), Cain, and the wandering Jew immediately occur to me. With a little thought I cold probably come up with more.
This group is sooo lovely, the level of development is awesome and it's super awesome that despite the concept + plot being really intricate and engaging, the group itself is more casual.
Are you going to have a time when the group closes its current opening (at a member count / date)?