Scar's brother

Mattias is Scar's older brother. Mattias committed a human transmutation, attempting to revive the woman that both he and his brother loved, and failed, leading to the birth of the homunculus Lust and his going crazy. When his sanity was lost, he began to seek the Philosopher's Stone to retry his failed attempt at a human transmutation. When he found out that the secret ingredient to the Stone was a mass of live humans, he marked his body with the transmutation symbols that were needed to absorb lives and become a walking talking Philosopher's Stone. The lives he used were the deceased's in the Ishvalan massacre. But when Mattias and Scar tried to flee from the mass killings, State Alchemist Zolf J. Kimblee pursued them, and used his alchemic powers to give Scar his unusual mark located on his forehead, and to amputate his right arm. Mattias dispatched Kimblee by robbing him of the power-enhancing Red Stone he was wielding, and then fused his own right arm (the arm with the symbols necessary for the first two portions of an alchemic transmutation - the understanding of an item's molecular composition, and the deconstruction of that matter) to Scar's body before dying.