Shadow Vault Kingslayer

When you cast Shadow Vault Kingslayer,
uncover 1 (Reveal the top card of target player's
library. You may cast it for its casting cost if it's a noncreature spell, otherwise put it on the bottom of its
owner's library.)
When Shadow Vault Kingslayer enters the battlefield, if you've cast a noncreature spell you
don't own this turn, destroy target legendary
creature or planeswalker.