Whenever Skarn, Lord of Damnation enters the battlefield or attacks, you may exile one creature card from a graveyard. If you do, create a token that's a copy of that card, except it's a black Demon in addition to its other types and it's under your control.

Sacrifice another Demon: Skarn, Lord of Damnation gets +2/+2 and gains indestructible until end of turn.

{B}{R}, {T}: Skarn deals damage to target creature equal to the number of Demons you control. If a non-Demon creature is dealt damage this way, it becomes a Demon in addition to its other types.