The secret of Imu's Devil Fruit lies in this immortality. To turn someone immortal, Imu takes a part of their lifespan or ...

The Rain God Devil Fruit might be a real One Piece fruit, and it might be in possession of a Yonko-level character.

Devil Fruits can come in all sorts of weird and whacky forms, but these are by far the silliest of the bunch in One Piece.