Abhorrent Overlord | Creature | Demon | Flying
When Abhorrent Overlord enters the battlefield, create a number of 1/1 black Harpy creature tokens with flying equal to your devotion to black. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)
At the beginning of your upkeep, sacrifice a creature. | Slawomir Maniak
Agent of the Fates | Creature | Human Assassin | Deathtouch
Heroic — Whenever you cast a spell that targets Agent of the Fates, each opponent sacrifices a creature. | Matt Stewart
Nighthowler | Enchantment Creature | Horror | Bestow {2}{B}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Nighthowler and enchanted creature each get +X/+X, where X is the number of creature cards in all graveyards. | Nils Hamm
Triad of Fates | Legendary Creature | Human Wizard | {1}, {T}: Put a fate counter on another target creature.
{W}, {T}: Exile target creature that has a fate counter on it, then return it to the battlefield under its owner's control.
{B}, {T}: Exile target creature that has a fate counter on it. Its controller draws two cards. | Daarken
Tymaret, the Murder King | Legendary Creature | Zombie Warrior | {1}{R}, Sacrifice another creature: Tymaret, the Murder King deals 2 damage to target player or planeswalker.
{1}{B}, Sacrifice a creature: Return Tymaret from your graveyard to your hand. | Volkan Baǵa
Reaper of the Wilds | Creature | Gorgon | Whenever another creature dies, scry 1. (Look at the top card of your library. You may put that card on the bottom of your library.)
{B}: Reaper of the Wilds gains deathtouch until end of turn.
{1}{G}: Reaper of the Wilds gains hexproof until end of turn. | Karl Kopinski