Bloodthrone Vampire

Sacrifice a creature: This creature gets +2/+2 until end of turn.

Bloodflow Connoisseur

Sacrifice a creature: Put a +1/+1 counter on this creature.

Martyr's Bond

Whenever this enchantment or another nonland permanent you control is put into a graveyard from the battlefield, each opponent sacrifices a permanent of their choice that shares a card type with it.

Gisela, the Broken Blade

Flying, first strike, lifelink
At the beginning of your end step, if you both own and control Gisela and a creature named Bruna, the Fading Light, exile them, then meld them into Brisela, Voice of Nightmares.

Overseer of the Damned

Flying
When this creature enters, you may destroy target creature.
Whenever a nontoken creature an opponent controls dies, create a tapped 2/2 black Zombie creature token.

Dictate of Erebos

Flash
Whenever a creature you control dies, each opponent sacrifices a creature of their choice.