The Fall of Kroog

Choose target opponent. Destroy target land that player controls. The Fall of Kroog deals 3 damage to that player and 1 damage to each creature they control.

Meria's Outrider

Reach
Domain — When Meria's Outrider enters, it deals damage to each opponent equal to the number of basic land types among lands you control.

Capricious Hellraiser

This spell costs {3} less to cast if you have nine or more cards in your graveyard.
Flying
When Capricious Hellraiser enters, exile three cards at random from your graveyard. Choose a noncreature, nonland card from among them and copy it. You may cast the copy without paying its mana cost.

Obliterating Bolt

Obliterating Bolt deals 4 damage to target creature or planeswalker. If that creature or planeswalker would die this turn, exile it instead.

Lambholt Ravager

Whenever you cast a noncreature spell, Lambholt Ravager deals 2 damage to each opponent.
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Lambholt Raconteur

Whenever you cast a noncreature spell, Lambholt Raconteur deals 1 damage to each opponent.
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Lambholt Raconteur // Lambholt Ravager

Kessig Flamebreather

Whenever you cast a noncreature spell, Kessig Flamebreather deals 1 damage to each opponent.

Call In a Professional

Players can't gain life this turn. Damage can't be prevented this turn. Call In a Professional deals 3 damage to any target. (Shield counters don't prevent this damage as they're removed.)

Mountain

Falkenrath Perforator

Whenever Falkenrath Perforator attacks, it deals 1 damage to defending player.

End the Festivities

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

Mishra's Foundry

{T}: Add {C}.
{2}: Mishra's Foundry becomes a 2/2 Assembly-Worker artifact creature until end of turn. It's still a land.
{1}, {T}: Target attacking Assembly-Worker gets +2/+2 until end of turn.

Unleash Shell

Unleash Shell deals 5 damage to target creature or planeswalker and 2 damage to that permanent's controller.

Pyrrhic Blast

As an additional cost to cast this spell, sacrifice a creature.
Pyrrhic Blast deals damage equal to the sacrificed creature's power to any target. Draw a card.

Lightning Strike

Lightning Strike deals 3 damage to any target.

Dire-Strain Anarchist

Menace, haste
Whenever Dire-Strain Anarchist attacks, it deals 2 damage to each of up to one target creature, up to one target player, and/or up to one target planeswalker.
Nightbound (If a player casts at least two spells during their own turn, it becomes day next turn.)

Volatile Arsonist

Menace, haste
Whenever Volatile Arsonist attacks, it deals 1 damage to each of up to one target creature, up to one target player, and/or up to one target planeswalker.
Daybound (If a player casts no spells during their own turn, it becomes night next turn.)

Volatile Arsonist // Dire-Strain Anarchist

Battlefield Forge

{T}: Add {C}.
{T}: Add {R} or {W}. Battlefield Forge deals 1 damage to you.

Koth, Fire of Resistance

+2: Search your library for a basic Mountain card, reveal it, put it into your hand, then shuffle.
−3: Koth, Fire of Resistance deals damage to target creature equal to the number of Mountains you control.
−7: You get an emblem with "Whenever a Mountain you control enters, this emblem deals 4 damage to any target."

Excavation Explosion

Excavation Explosion deals 3 damage to any target. Create a tapped Powerstone token. (It's an artifact with "{T}: Add {C}. This mana can't be spent to cast a nonartifact spell.")