Plague Reaver

At the beginning of your end step, sacrifice each other creature you control.
Discard two cards, Sacrifice Plague Reaver: Choose target opponent. Return Plague Reaver to the battlefield under that player's control at the beginning of their next upkeep.

Desecration Elemental

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Whenever a player casts a spell, sacrifice a creature.

Wretched Anurid

Whenever another creature enters, you lose 1 life.

Drinker of Sorrow

Drinker of Sorrow can't block.
Whenever Drinker of Sorrow deals combat damage, sacrifice a permanent.

Ebon Drake

Flying
Whenever a player casts a spell, you lose 1 life.

Phyrexian Negator

Trample
Whenever Phyrexian Negator is dealt damage, sacrifice that many permanents.

Jon Irenicus, Shattered One

At the beginning of your end step, target opponent gains control of up to one target creature you control. Put two +1/+1 counters on it and tap it. It's goaded for the rest of the game and it gains "This creature can't be sacrificed." (It attacks each combat if able and attacks a player other than you if able.)
Whenever a creature you own but don't control attacks, you draw a card.

Steel Golem

Rust Elemental

Flying
At the beginning of your upkeep, sacrifice an artifact other than Rust Elemental. If you can't, tap Rust Elemental and you lose 4 life.

Flesh Reaver

Whenever Flesh Reaver deals damage to a creature or opponent, Flesh Reaver deals that much damage to you.

Archfiend of the Dross

Flying
Archfiend of the Dross enters with four oil counters on it.
At the beginning of your upkeep, remove an oil counter from Archfiend of the Dross. Then if it has no oil counters on it, you lose the game.
Whenever a creature an opponent controls dies, its controller loses 2 life.

Abyssal Persecutor

Flying, trample
You can't win the game and your opponents can't lose the game.

Rotting Regisaur

At the beginning of your upkeep, discard a card.

Master of the Feast

Flying
At the beginning of your upkeep, each opponent draws a card.

Greater Harvester

At the beginning of your upkeep, sacrifice a permanent.
Whenever Greater Harvester deals combat damage to a player, that player sacrifices two permanents of their choice.

Demonic Taskmaster

Flying
At the beginning of your upkeep, sacrifice a creature other than Demonic Taskmaster.