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.

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.)

Wizard's Lightning

This spell costs {2} less to cast if you control a Wizard.
Wizard's Lightning deals 3 damage to any target.

Obsessive Astronomer

If it's neither day nor night, it becomes day as Obsessive Astronomer enters.
Whenever day becomes night or night becomes day, discard up to two cards, then draw that many cards.

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Mountain

Moonrager's Slash

This spell costs {2} less to cast if it's night.
Moonrager's Slash deals 3 damage to any target.

Lava Spike

Lava Spike deals 3 damage to target player or planeswalker.

Flame Rift

Flame Rift deals 4 damage to each player.

Ghitu Lavarunner

As long as there are two or more instant and/or sorcery cards in your graveyard, this creature gets +1/+0 and has haste. (It can attack and {T} as soon as it comes under your control.)

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.