King's Costume Ball

At the beginning of your upkeep, choose one that hasn't been chosen --
* All creatures are legendary until your next turn.
* Choose a creature type. Each creature is the chosen type until your next turn.
* Target creature becomes the copy of another target creature until your next turn.
* Each player chooses a creature he or she controls, then return all other creatures to their owners' hands. Sacrifice King's Costume Ball.