Sirens (Borderlands)

In the Borderlands universe, some of the most powerful characters are the Sirens - women enhanced with magical powers, who are born with strange tattoos that cover their bodies. Not a whole lot is known about the Sirens, except that only six can exist in the universe at any given time (according to Handsome Jack, anyway), and they have some kind of connection to the Eridians and the Vaults.