From Viz:
A born exorcist, Walker's primary anti-akuma weapon is the cross that's embossed on his red, disfigured left hand, which contains Innocence. But not only does Walker destroy akuma, he sees the akuma hiding inside a person's soul! Together with his fellow exorcists fighting under the command of the Black Order, Walker leads the battle against the Millennium Earl, the evil being out to destroy mankind.