
Chaos Imps | Creature | Imp | Flying
Unleash (You may have this creature enter the battlefield with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)
Chaos Imps has trample as long as it has a +1/+1 counter on it. | Tyler Jacobson

Guild Feud | Enchantment | | At the beginning of your upkeep, target opponent reveals the top three cards of their library, may put a creature card from among them onto the battlefield, then puts the rest into their graveyard. You do the same with the top three cards of your library. If two creatures are put onto the battlefield this way, those creatures fight each other. | Karl Kopinski

Carnival Hellsteed | Creature | Nightmare Horse | First strike, haste
Unleash (You may have this creature enter the battlefield with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.) | Chase Stone

Havoc Festival | Enchantment | | Players can't gain life.
At the beginning of each player's upkeep, that player loses half their life, rounded up. | Johannes Voss