Ob Nixilis, the Adversary

Casualty X. The copy isn't legendary and has starting loyalty X. (As you cast this spell, you may sacrifice a creature with power X. When you do, copy this spell. The copy becomes a token.)
[+1]: Each opponent loses 2 life unless they discard a card. If you control a Demon or Devil, you gain 2 life.
[−2]: Create a 1/1 red Devil creature token with "When this token dies, it deals 1 damage to any target."
[−7]: Target player draws seven cards and loses 7 life.