Chain Reaction

Chain Reaction deals X damage to each creature, where X is the number of creatures on the battlefield.

Blackblade Reforged

Equipped creature gets +1/+1 for each land you control.
Equip legendary creature {3}
Equip {7}

Munitions Expert

Flash
When this creature enters, you may have it deal damage to target creature or planeswalker equal to the number of Goblins you control.

Wrecking Ball

Mountain Goat

Mountainwalk (This creature can't be blocked as long as defending player controls a Mountain.)

Totentanz, Swarm Piper

Whenever Totentanz or another nontoken creature you control dies, create a 1/1 black Rat creature token with "This token can't block."
{1}{B}: Target attacking Rat you control gains deathtouch until end of turn.

Mountain

Terminate

Destroy target creature. It can't be regenerated.

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

Rakdos Ragemutt

Diabolic Edict

Target player sacrifices a creature of their choice.

Heartless Act

Choose one —
• Destroy target creature with no counters on it.
• Remove up to three counters from target creature.

Mayhem Devil

Whenever a player sacrifices a permanent, this creature deals 1 damage to any target.

Ashenmoor Liege

Other black creatures you control get +1/+1.
Other red creatures you control get +1/+1.
Whenever this creature becomes the target of a spell or ability an opponent controls, that player loses 4 life.

Swamp

Infernal Grasp

Destroy target creature. You lose 2 life.

Underworld Cerberus

This creature can't be blocked except by three or more creatures.
Cards in graveyards can't be the targets of spells or abilities.
When this creature dies, exile it and each player returns all creature cards from their graveyard to their hand.

Mogis, God of Slaughter

Indestructible
As long as your devotion to black and red is less than seven, Mogis isn't a creature.
At the beginning of each opponent's upkeep, Mogis deals 2 damage to that player unless they sacrifice a creature of their choice.

Rakdos Charm

Choose one —
• Exile target player's graveyard.
• Destroy target artifact.
• Each creature deals 1 damage to its controller.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Vessel of Volatility

{1}{R}, Sacrifice this enchantment: Add {R}{R}{R}{R}.

Auger Spree

Target creature gets +4/-4 until end of turn.

Wring Flesh

Target creature gets -3/-1 until end of turn.

Koth of the Hammer

+1: Untap target Mountain. It becomes a 4/4 red Elemental creature until end of turn. It's still a land.
−2: Add {R} for each Mountain you control.
−5: You get an emblem with "Mountains you control have '{T}: This land deals 1 damage to any target.'"