Rakdos Cackler

Unleash (You may have this creature enter with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)

Dreadhorde Butcher

Haste
Whenever this creature deals combat damage to a player or planeswalker, put a +1/+1 counter on this creature.
When this creature dies, it deals damage equal to its power to any target.

Smoldering Marsh

({T}: Add {B} or {R}.)
This land enters tapped unless you control two or more basic lands.

Sign in Blood

Target player draws two cards and loses 2 life.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Spawn of Mayhem

Spectacle {1}{B}{B} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Flying, trample
At the beginning of your upkeep, this creature deals 1 damage to each player. Then if you have 10 or less life, put a +1/+1 counter on this creature.

Swamp

Dragonskull Summit

This land enters tapped unless you control a Swamp or a Mountain.
{T}: Add {B} or {R}.

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Terminate

Destroy target creature. It can't be regenerated.

Mountain

Cryptborn Horror

Trample
This creature enters with X +1/+1 counters on it, where X is the total life lost by your opponents this turn.

Fulminator Mage

Sacrifice this creature: Destroy target nonbasic land.

Blood Moon

Rakdos, Lord of Riots

You can't cast Rakdos unless an opponent lost life this turn.
Flying, trample
Creature spells you cast cost {1} less to cast for each 1 life your opponents have lost this turn.