Dark Energy Gate

(This card enters your mana zone tapped.)
{s}Shield Blast (Instead of putting this spell into your
hand from a broken shield, you may cast it for free.)
All of your creatures get "Slayer" until the end
of the turn. (When a creature that has "Slayer"
loses a battle, banish the other creature.)
Put the top card of your deck into your mana
zone.
Purify them all.