Mark of the Oni

Enchant creature
You control enchanted creature.
At the beginning of the end step, if you control no Demons, sacrifice Mark of the Oni.

Blood Speaker

At the beginning of your upkeep, you may sacrifice Blood Speaker. If you do, search your library for a Demon card, reveal that card, put it into your hand, then shuffle.
Whenever a Demon enters under your control, return Blood Speaker from your graveyard to your hand.

Oni Possession

Enchant creature
At the beginning of your upkeep, sacrifice a creature.
Enchanted creature gets +3/+3 and has trample.
Enchanted creature is a Demon Spirit.

Gutwrencher Oni

Trample
At the beginning of your upkeep, discard a card if you don't control an Ogre.

Raving Oni-Slave

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

Swamp

Yukora, the Prisoner

When Yukora, the Prisoner leaves the battlefield, sacrifice all non-Ogre creatures you control.

Kuro, Pitlord

At the beginning of your upkeep, sacrifice Kuro, Pitlord unless you pay {B}{B}{B}{B}.
Pay 1 life: Target creature gets -1/-1 until end of turn.

Scourge of Numai

At the beginning of your upkeep, you lose 2 life if you don't control an Ogre.

Tomb of Urami

{T}: Add {B}. Tomb of Urami deals 1 damage to you if you don't control an Ogre.
{2}{B}{B}, {T}, Sacrifice all lands you control: Create Urami, a legendary 5/5 black Demon Spirit creature token with flying.

Painwracker Oni

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
At the beginning of your upkeep, sacrifice a creature if you don't control an Ogre.

Hellcarver Demon

Flying
Whenever Hellcarver Demon deals combat damage to a player, sacrifice all other permanents you control and discard your hand. Exile the top six cards of your library. You may cast any number of spells from among cards exiled this way without paying their mana costs.

Bloodthirsty Ogre

{T}: Put a devotion counter on Bloodthirsty Ogre.
{T}: Target creature gets -X/-X until end of turn, where X is the number of devotion counters on Bloodthirsty Ogre. Activate only if you control a Demon.

Villainous Ogre

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

Seizan, Perverter of Truth

At the beginning of each player's upkeep, that player loses 2 life and draws two cards.

Ogre Marauder

Whenever Ogre Marauder attacks, it gains "Ogre Marauder can't be blocked" until end of turn unless defending player sacrifices a creature of their choice.

Kyoki, Sanity's Eclipse

Whenever you cast a Spirit or Arcane spell, target opponent exiles a card from their hand.

Razorjaw Oni

Takenuma Bleeder

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