Fleshbag Marauder

When Fleshbag Marauder enters, each player sacrifices a creature.

Plaguecrafter

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

Merciless Executioner

When Merciless Executioner enters, each player sacrifices a creature.

Demon's Disciple

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

Meren of Clan Nel Toth

Whenever another creature you control dies, you get an experience counter.
At the beginning of your end step, choose target creature card in your graveyard. If that card's mana value is less than or equal to the number of experience counters you have, return it to the battlefield. Otherwise, put it into your hand.