Deep Destiny

Enchant creature
Enchanted creature gets +4/+4, has
trample and "Discard two cards: Exile this
creature and Deep Destiny. Return it to the battlefield tapped under its owner's control at the
beginning of the next end step, then return Deep Destiny to the battlefield attached to it". It's a Leviathan in addition to its other types.
When enchanted creature dies, return
Deep Destiny to its owner's hand.