The Bell of Oblivion is a clocktower bell located in the town of Lostime. Whenever it rings, one citizen forgets something important.
The Bell of Oblivion was created years ago to ease the townspeople of their suffering caused by the Destroyer. It sealed the memories away, weakening the monster and gave the Guardian Beasts the chance to seal it away as well.
Years later, Cid and Chocobo arrived, the bell first rang, erasing Cid's memories. Shirma came and took them away from the town before the bell rings again. When Raffaello was born, the curse of the bell began to waver as the boy, teamed with Chocobo, restore the townspeople's memories.
After the Destroyer is defeated, the Bell of Oblivion ceases its effect and returns to its original state.
"Oblivion" is a state of complete forgetfulness, especially the permanent lack of consciousness following death.