Nidhogg, Tree's Destroyer

Flying, Trample
When Nidhogg the Destroyer deals combat
damage to a player, reveal the top X cards of
your library, you may put a permanent with
converted mana cost X or less from among
them onto the battlefield, then destroy target
permanent with X converted mana cost,
where X is the amount of damage Nidhogg,
tree's Destroyer dealt.