Made to counter its Johto counterpart, Atroci Corp. has engineered this pokemon to push the original Tyranitar to its limits for studies of the creature's true power. It's developed an odd mutation of growing a second, almost fully-functioning, head from the tail. Because of this mutation, some scientists have given it the nickname "Shin Tyranitar" rather than its official "Atroci-1".
--Yako Xen