Berthold Hawkeye

Master Berthold Hawkeye was both the alchemist who mentored Roy Mustang as well as the estranged father of Riza Hawkeye.

A brilliant alchemist, Hawkeye postulated the complex and intricate theorems necessary to apply flame alchemy at its most powerful and efficient level, but refused to pass on his flame alchemy secrets to his pupil, thinking them to be too dangerous for the young and naive Roy. Riza describes her father as a frightening man with whom she did not generally associate and could not at all relate. Afraid of his life's work being destroyed and what his Flame Alchemy knowledge could do if it fell into the wrong hands, he refrained from keeping notes in the normal fashion and, instead, tattooed a large Transmutation Array containing the culmination of his craft and findings on his daughter's back, perhaps further straining - or serving as an indication of - their already shaky relationship.

Master Hawkeye, as an independent alchemist, appears to hold some disdain for the State Military (much like Izumi Curtis), as revealed by his flippant reaction to Roy's enlistment during the Ishval Civil War as well as his preference of living in squalor with all his genius over joining the State Alchemist Program.

As Roy returned to his teacher's house in an attempt to get hold of the theory of Flame Alchemy to enlist as a State Alchemist (he was just a regular soldier at that time), Master Hawkeye revealed to him his daughter possessed the theory and succumbed to illness, coughing up blood as he died in his arms.

Trivia

 * While Master Hawkeye's first name was never given in the manga, Fullmetal Alchemist: Brotherhood's 30th episode states his name and birth year upon his tombstone.
 * Master Hawkeye slightly resembles Shimei, an antagonist from Arakawa's manga series Hero Tales.
 * Berthold Hawkeye may most likely have gained his given name from Berthold Schwartz, or Black Berthold, a German alchemist of the thirteenth or fourteenth century who is said to have discovered gunpowder and the cannon. He was sometimes nicknamed the "Powder Monk".