Event Horizon

Celestial spells you cast cost {2} less.
Colored spells opponents cast cost {2} more.
When a creature attacks you or a Planeswalker
you control, exile it at the end of combat. At the beginning of each end step, if there are ten or
more creature in a exile you may pay {10} and
sacrifice Event Horizon then return all creatures
in exile to the battlefield tapped under your
control.