War of the Spark

Dreadhorde Butcher | Creature | Zombie Warrior | Haste Whenever Dreadhorde Butcher deals combat damage to a player or planeswalker, put a +1/+1 counter on Dreadhorde Butcher. When Dreadhorde Butcher dies, it deals damage equal to its power to any target. | Piotr Dura

Mayhem Devil | Creature | Devil | Whenever a player sacrifices a permanent, Mayhem Devil deals 1 damage to any target. | Dmitry Burmak

Niv-Mizzet Reborn | Legendary Creature | Dragon Avatar | Flying When Niv-Mizzet Reborn enters the battlefield, reveal the top ten cards of your library. For each color pair, choose a card that's exactly those colors from among them. Put the chosen cards into your hand and the rest on the bottom of your library in a random order. | Raymond Swanland