Raving Oni-Slave

When Raving Oni-Slave enters or leaves the battlefield, you lose 3 life if you don't control a Demon.

Awoken Demon

Ecstatic Awakener

{2}{B}, Sacrifice another creature: Draw a card, then transform Ecstatic Awakener. Activate only once each turn.

Ecstatic Awakener // Awoken Demon

Villainous Ogre

Villainous Ogre can't block.
As long as you control a Demon, Villainous Ogre has "{B}: Regenerate Villainous Ogre."

Demon's Jester

Flying
Hellbent — Demon's Jester gets +2/+1 as long as you have no cards in hand.

Scroll of Griselbrand

{1}, Sacrifice Scroll of Griselbrand: Target opponent discards a card. If you control a Demon, that player loses 3 life.

Shadowborn Apostle

A deck can have any number of cards named Shadowborn Apostle.
{B}, Sacrifice six creatures named Shadowborn Apostle: Search your library for a Demon creature card, put it onto the battlefield, then shuffle.

Rafter Demon

Spectacle {3}{B}{R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
When Rafter Demon enters, if its spectacle cost was paid, each opponent discards a card.

Takenuma Bleeder

Whenever Takenuma Bleeder attacks or blocks, you lose 1 life if you don't control a Demon.