Formerly the Crystal Alchemist, Marcoh was the leading researcher in the creation of the Philosopher's Stone. Tormented by the fact that his research was used in the Ishval War to kill many innocent people, he fled from his position as a State Alchemist and took his research with him to prevent it from being used for further destruction. Hiding from the military and posing as a medical doctor, he uses the Red Stone he created to help the sick.