Wrath makes his first appearance on FMA in episode 28. He shows up on the small island where the Elric brothers were tested by their sensei, Izumi. Izumi is immediately drawn to the child. As it turns out, Wrath is a homunculus. He is the product of Izumi's failed attempt at bringing life to her unborn baby. In other words...a failed human transmutation. What's even more shocking is Wrath's right arm and left leg are Edward Elric's missing limbs. This is why Wrath is a homunculus who CAN use alchemy.

When united with the other homunculus, Wrath builds a strong bond with Sloth. He is convinced that she is his mother. Well, he's half right--(ha, ha, get it?....he's part of Ed and....you know....).