Foreboding Ruins

As this land enters, you may reveal a Swamp or Mountain card from your hand. If you don't, this land enters tapped.
{T}: Add {B} or {R}.

Ob Nixilis, Captive Kingpin

Flying, trample
Whenever one or more opponents each lose exactly 1 life, put a +1/+1 counter on Ob Nixilis. Exile the top card of your library. Until your next end step, you may play that card.

Cavalcade of Calamity

Whenever a creature you control with power 1 or less attacks, this enchantment deals 1 damage to the player or planeswalker that creature is attacking.

Spiteful Prankster

During your turn, this creature has first strike.
Whenever another creature dies, this creature deals 1 damage to target player or planeswalker.

Village Rites

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Dance with Devils

Create two 1/1 red Devil creature tokens. They have "When this token dies, it deals 1 damage to any target."

Vicious Rumors

Vicious Rumors deals 1 damage to each opponent. Each opponent discards a card, then mills a card. You gain 1 life.

Mountain

Theater of Horrors

At the beginning of your upkeep, exile the top card of your library.
During your turn, if an opponent lost life this turn, you may play lands and cast spells from among cards exiled with this enchantment.
{3}{R}: This enchantment deals 1 damage to target opponent or planeswalker.

Tectonic Hazard

Tectonic Hazard deals 1 damage to each opponent and each creature they control.

Witty Roastmaster

Alliance — Whenever another creature you control enters, this creature deals 1 damage to each opponent.

Torch Fiend

{R}, Sacrifice this creature: Destroy target artifact.

Make Mischief

Make Mischief deals 1 damage to any target. Create a 1/1 red Devil creature token. It has "When this token dies, it deals 1 damage to any target."

Devil's Play

Devil's Play deals X damage to any target.
Flashback {X}{R}{R}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Footlight Fiend

When this creature dies, it deals 1 damage to any target.

Burn Down the House

Choose one —
• Burn Down the House deals 5 damage to each creature and each planeswalker.
• Create three 1/1 red Devil creature tokens with "When this token dies, it deals 1 damage to any target." They gain haste until end of turn.

Tibalt's Rager

When this creature dies, it deals 1 damage to any target.
{1}{R}: This creature gets +2/+0 until end of turn.

Mayhem Devil

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

Bedevil

Destroy target artifact, creature, or planeswalker.

Smoldering Marsh

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

Body Dropper

Whenever you sacrifice another creature, put a +1/+1 counter on this creature.
{B}{R}, Sacrifice another creature: This creature gains menace until end of turn. (It can't be blocked except by two or more creatures.)

Swamp

Devils' Playground

Create four 1/1 red Devil creature tokens. They have "When this token dies, it deals 1 damage to any target."