Fleshbag Marauder

When Fleshbag Marauder enters, each player sacrifices a creature.

Helm of Possession

You may choose not to untap Helm of Possession during your untap step.
{2}, {T}, Sacrifice a creature: Gain control of target creature for as long as you control Helm of Possession and Helm of Possession remains tapped.

Bontu's Monument

Black creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, each opponent loses 1 life and you gain 1 life.

Hazoret's Monument

Red creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, you may discard a card. If you do, draw a card.

Merciless Executioner

When Merciless Executioner enters, each player sacrifices a creature.

Mogis, God of Slaughter

Indestructible
As long as your devotion to black and red is less than seven, Mogis isn't a creature.
At the beginning of each opponent's upkeep, Mogis deals 2 damage to that player unless they sacrifice a creature.

Rakdos Signet

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Demon's Disciple

When Demon's Disciple enters, each player sacrifices a creature or planeswalker.

Ruby Medallion

Red spells you cast cost {1} less to cast.

Plaguecrafter

When Plaguecrafter enters, each player sacrifices a creature or planeswalker. Each player who can't discards a card.