Marcoh was the Crystal Alchemist and the State's top researcher on Philosopher's Stones—until the guilt caught up with him. When he realized his work had been weaponized during the Ishval War, killing countless civilians, he couldn't stay. He deserted his position, grabbed his research, and disappeared into hiding, determined to keep it out of military hands.
These days he poses as a medical doctor and uses a Red Stone of his own creation to treat patients. It's basically his attempt at redemption—using alchemy to heal instead of destroy, at least for the people he can actually reach.
Content compiled by AnimeList.moe from publicly available sources.
