When several members of the Callasantos family died, Lucia and her sister Maria, joined the Morlocks, a group of mutants living in sewer tunnels. Later, when Maria (Feral) joined X-Force, Lucia faced her sister, now as a member of the Brotherhood of Mutants. X-Force won the battle and Thornn left the Brotherhood.
Years later, Thornn and Feral joined the X-Corporation, an organization founded by Chales Xavier. Following the event known as House of M|M-Day, the two sisters lost their powers. Recently, Thornn and Feral had their lupine appearance restored when they, along with Sasquatch and Wolfsbane, helped Wolverine fight against Sabretooth, Feral was killed in the process. Thornn was left in a state of shock when last we saw her.