The Betrayer, God Slayer

Indestructible, hexproof
Whenever you cast a spell, put a
Shadowtouched counter on target creature.
Creatures with Shadowtouched get -4/-4 and
"When this creature dies, you lose 5 life."
If a card would go to a graveyard, instead exile it.
You may cast any card exiled this way. Whenever
an opponent loses life, you may discard the top
card of their library