Eidolon of the Great Revel

Whenever a player casts a spell with mana value 3 or less, this creature deals 2 damage to that player.

Void Mirror

Whenever a player casts a spell, if no colored mana was spent to cast it, counter that spell.

Lava Spike

Lava Spike deals 3 damage to target player or planeswalker.

Vexing Devil

When this creature enters, any opponent may have it deal 4 damage to them. If a player does, sacrifice this creature.

Goblin Guide

Haste
Whenever this creature attacks, defending player reveals the top card of their library. If it's a land card, that player puts it into their hand.

Tormod's Crypt

{T}, Sacrifice this artifact: Exile target player's graveyard.

Light Up the Stage

Spectacle {R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Exile the top two cards of your library. Until the end of your next turn, you may play those cards.

Smash to Smithereens

Destroy target artifact. Smash to Smithereens deals 3 damage to that artifact's controller.

Fireblast

You may sacrifice two Mountains rather than pay this spell's mana cost.
Fireblast deals 4 damage to any target.

Monastery Swiftspear

Haste
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Searing Blood

Searing Blood deals 2 damage to target creature. When that creature dies this turn, Searing Blood deals 3 damage to the creature's controller.

Skullcrack

Players can't gain life this turn. Damage can't be prevented this turn. Skullcrack deals 3 damage to target player or planeswalker.

Skewer the Critics

Spectacle {R} (You may cast this spell for its spectacle cost rather than its mana cost if an opponent lost life this turn.)
Skewer the Critics deals 3 damage to any target.

Mountain

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Rift Bolt

Rift Bolt deals 3 damage to any target.
Suspend 1—{R} (Rather than cast this card from your hand, you may pay {R} and exile it with a time counter on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)

Chain Lightning

Chain Lightning deals 3 damage to any target. Then that player or that permanent's controller may pay {R}{R}. If the player does, they may copy this spell and may choose a new target for that copy.