9x36 - Fairy Tail

In a flashback to the Dragon King Festival, Irene rules a kingdom where humans and dragons peacefully co-exist against dragons who devour humans. Hoping to gain an advantage in the war, Irene uses her powers of enchantment to create Dragon Slayer magic for humans, which inadvertently turns Acnologia into a dragon and eradicates most of the species. After conceiving Erza, Irene begins changing into a dragon as well, and is subsequently imprisoned and tortured by her paranoid husband; to protect their unborn daughter, Irene magically halts Erza's growth in her womb for years. When her husband threatens Erza, Irene fully transforms and kills him before fleeing into isolation. Centuries later, Zeref discovers Irene and restores her original appearance, but cannot restore her humanity. Driven insane by her inability to adjust to human sensations, Irene attempts to become human again by enchanting her own consciousness onto Erza.