simple 2 creature kill

Flying When this creature enters, sacrifice it unless you return an enchantment to its owner's hand.

When this creature enters, return a permanent you control to its owner's hand.

Enchant permanent Vanishing 3 (This Aura enters with three time counters on it. At the beginning of your upkeep, remove a time counter from it. When the last is removed, sacrifice it.) When this Aura leaves the battlefield, enchanted permanent's controller sacrifices it.