Wrath is a Homunculus who was created when Izumi Curtis tried to revive her infant child. Though Wrath had still been trapped in the Gate of Truth, until the Elric Brothers tried to bring their mother back to life, which failed, causing Ed to loose his arm, and his leg. Though Wrath then ceased the opportunity, and obtained Eds limbs, and use Alchemy to break free of the Gate of Truth. In addition to using Alchemy, Wrath can merge with any object he pleases. Also because he is the remains of his former body, he cannot be weakened like his fellow Homunculi, but the cries of children have a similar effect.
After joining the Humunculi after being tricked or convinced that he wants to become human, and Izumi, and the other are bad, he finds a mother figure in sloth.