When several members of Callasantos's family died, Lucia and her sister Maria, joined the Morlocks, a group of mutants based on sewer tunnels. Times later, when Maria (Feral) joined X-Force, Lucia faced her sister, now as member of the Brotherhood of Mutants. X-Force win and Thornn left the Brotherhood.

Years later, Thornn and Feral joined the X-Corporation, a organization founded by Chales Xavier. Following the M-Day, the two sisters lost the powers. Recently, Thornn and Feral had the lupine appearance restored when they and others helped Wolverine against Sabretooth, that killed Feral in the process. Thornn is in shock.