Sarkyn, Lich Master

Deathtouch, Lifelink, Trample
Whenever Sarkyn, Lich Master causes you to gain
life, you may pay that much life. If you do,
destroy target creature with converted mana cost
X or less, where X is the amount of life you paid.
"You are nothing but a lone soul wandering
in the endless maze of life. And I guard the only
exit."