Shattercast Occultist

Lifelink, decayed (This creature can't block. When
it attacks, sacrifice it at the end of combat.)
As an additional cost to cast a black instant or
sorcery spell, you may sacrifice Shattercast
Occultist. If you do, exile it. That spell can't
be countered, and it gains "whenever a player
loses life this way, exile that many cards from
the top of their library"