Meltdown

Destroy each artifact with mana value X or less.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Surgical Extraction

({B/P} can be paid with either {B} or 2 life.)
Choose target card in a graveyard other than a basic land card. Search its owner's graveyard, hand, and library for any number of cards with the same name as that card and exile them. Then that player shuffles.

Vexing Devil

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

Burn Together

Target creature you control deals damage equal to its power to any other target. Then sacrifice it.

Callous Sell-Sword

Callous Sell-Sword enters with a +1/+1 counter on it for each creature that died under your control this turn.

Callous Sell-Sword // Burn Together

Monstrous Rage

Target creature gets +2/+0 until end of turn. Create a Monster Role token attached to it. (If you control another Role on it, put that one into the graveyard. Enchanted creature gets +1/+1 and has trample.)

Mutagenic Growth

({G/P} can be paid with either {G} or 2 life.)
Target creature gets +2/+2 until end of turn.

Kiln Fiend

Whenever you cast an instant or sorcery spell, Kiln Fiend gets +3/+0 until end of turn.

Relic of Progenitus

{T}: Target player exiles a card from their graveyard.
{1}, Exile Relic of Progenitus: Exile all graveyards. Draw a card.

End the Festivities

End the Festivities deals 1 damage to each opponent and each creature and planeswalker they control.

Monastery Swiftspear

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

Slickshot Show-Off

Flying, haste
Whenever you cast a noncreature spell, Slickshot Show-Off gets +2/+0 until end of turn.
Plot {1}{R} (You may pay {1}{R} and exile this card from your hand. Cast it as a sorcery on a later turn without paying its mana cost. Plot only as a sorcery.)

Gut Shot

({R/P} can be paid with either {R} or 2 life.)
Gut Shot deals 1 damage to any target.

Lava Dart

Lava Dart deals 1 damage to any target.
Flashback—Sacrifice a Mountain. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Pyroclasm

Pyroclasm deals 2 damage to each creature.

Lava Spike

Lava Spike deals 3 damage to target player or planeswalker.

Soul-Scar Mage

Prowess
If a source you control would deal noncombat damage to a creature an opponent controls, put that many -1/-1 counters on that creature instead.

Sunbaked Canyon

{T}, Pay 1 life: Add {R} or {W}.
{1}, {T}, Sacrifice Sunbaked Canyon: Draw a card.

Mountain

Cast into the Fire

Choose one —
• Cast into the Fire deals 1 damage to each of up to two target creatures.
• Exile target artifact.

Fiery Islet

{T}, Pay 1 life: Add {U} or {R}.
{1}, {T}, Sacrifice Fiery Islet: Draw a card.

Eidolon of the Great Revel

Whenever a player casts a spell with mana value 3 or less, Eidolon of the Great Revel deals 2 damage to that player.