Shenanigans

Destroy target artifact.
Dredge 1 (If you would draw a card, you may mill a card instead. If you do, return this card from your graveyard to your hand.)

Harnfel, Horn of Bounty

Discard a card: Exile the top two cards of your library. You may play those cards this turn.

Birgi, God of Storytelling

Whenever you cast a spell, add {R}. Until end of turn, you don't lose this mana as steps and phases end.
Creatures you control can boast twice during each of your turns rather than once.

Birgi, God of Storytelling // Harnfel, Horn of Bounty

Grapeshot

Grapeshot deals 1 damage to any target.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Nivmagus Elemental

Exile an instant or sorcery spell you control: Put two +1/+1 counters on Nivmagus Elemental. (That spell won't resolve.)

Warlord's Fury

Creatures you control gain first strike until end of turn.
Draw a card.

Footlight Fiend

When Footlight Fiend dies, it 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.)

Gorilla Shaman

{X}{X}{1}: Destroy target noncreature artifact with mana value X.

Blistercoil Weird

Whenever you cast an instant or sorcery spell, Blistercoil Weird gets +1/+1 until end of turn. Untap it.

Satyr's Cunning

Create a 1/1 red Satyr creature token with "This creature can't block."
Escape—{2}{R}, Exile two other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)

Manamorphose

Add two mana in any combination of colors.
Draw a card.

Runaway Steam-Kin

Whenever you cast a red spell, if Runaway Steam-Kin has fewer than three +1/+1 counters on it, put a +1/+1 counter on Runaway Steam-Kin.
Remove three +1/+1 counters from Runaway Steam-Kin: Add {R}{R}{R}.

Scar

Bloodbraid Marauder

Bloodbraid Marauder can't block.
Delirium — This spell has cascade as long as there are four or more card types among cards in your graveyard. (When you cast this spell, exile cards from the top of your library until you exile a nonland card that costs less. You may cast it without paying its mana cost. Put the exiled cards on the bottom in a random order.)

Fossil Find

Return a card at random from your graveyard to your hand, then reorder your graveyard as you choose.

Goblin Bombardment

Sacrifice a creature: Goblin Bombardment deals 1 damage to any target.

Mountain

Dragon's Rage Channeler

Whenever you cast a noncreature spell, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)
Delirium — As long as there are four or more card types among cards in your graveyard, Dragon's Rage Channeler gets +2/+2, has flying, and attacks each combat if able.

Desperate Ritual

Add {R}{R}{R}.
Splice onto Arcane {1}{R} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Guttural Response

Lightning Bolt

Lightning Bolt deals 3 damage to any target.

Gut Shot

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

Dual Strike

When you next cast an instant or sorcery spell with mana value 4 or less this turn, copy that spell. You may choose new targets for the copy.
Foretell {R} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Bloodthirsty Adversary

Haste
When Bloodthirsty Adversary enters, you may pay {2}{R} any number of times. When you pay this cost one or more times, put that many +1/+1 counters on Bloodthirsty Adversary, then exile up to that many target instant and/or sorcery cards with mana value 3 or less from your graveyard and copy them. You may cast any number of the copies without paying their mana costs.

Moonveil Regent

Flying
Whenever you cast a spell, you may discard your hand. If you do, draw a card for each of that spell's colors.
When Moonveil Regent dies, it deals X damage to any target, where X is the number of colors among permanents you control.

Frostburn Weird

{U/R}: Frostburn Weird gets +1/-1 until end of turn.

Goblin Bushwhacker

Kicker {R} (You may pay an additional {R} as you cast this spell.)
When this creature enters, if it was kicked, creatures you control get +1/+0 and gain haste until end of turn.

Strike It Rich

Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Transguild Courier

Duergar Assailant

Sacrifice Duergar Assailant: It deals 1 damage to target attacking or blocking creature.

Kalain, Reclusive Painter

When Kalain, Reclusive Painter enters, create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Other creatures you control enter with an additional +1/+1 counter on them for each mana from a Treasure spent to cast them.

Grim Lavamancer

{R}, {T}, Exile two cards from your graveyard: Grim Lavamancer deals 2 damage to any target.

Manaforge Cinder

{1}: Add {B} or {R}. Activate no more than three times each turn.

Asmoranomardicadaistinaculdacar

As long as you've discarded a card this turn, you may pay {B/R} to cast this spell.
When Asmoranomardicadaistinaculdacar enters, you may search your library for a card named The Underworld Cookbook, reveal it, put it into your hand, then shuffle.
Sacrifice two Foods: Target creature deals 6 damage to itself.

Regal Leosaur

Mutate {1}{R/W}{R/W} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Whenever this creature mutates, other creatures you control get +2/+1 until end of turn.

Flame Jab

Flame Jab deals 1 damage to any target.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Wooded Foothills

{T}, Pay 1 life, Sacrifice Wooded Foothills: Search your library for a Mountain or Forest card, put it onto the battlefield, then shuffle.

Burning-Tree Emissary

When Burning-Tree Emissary enters, add {R}{G}.

Make Your Mark

Target creature gets +1/+0 until end of turn. When that creature dies this turn, create a 3/2 red and white Spirit creature token.

Sootstoke Kindler

Haste
{T}: Target black or red creature gains haste until end of turn.

Crash Through

Creatures you control gain trample until end of turn. (Each of those creature can deal excess combat damage to the player or planeswalker it's attacking.)
Draw a card.

Blazing Rootwalla

{R}: Blazing Rootwalla gets +2/+0 until end of turn. Activate only once each turn.
Madness {0} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Wild Cantor

({R/G} can be paid with either {R} or {G}.)
Sacrifice Wild Cantor: Add one mana of any color.

Illustrious Historian

{5}, Exile Illustrious Historian from your graveyard: Create a tapped 3/2 red and white Spirit creature token.

Spiteflame Witch

Bloodstained Mire

{T}, Pay 1 life, Sacrifice Bloodstained Mire: Search your library for a Swamp or Mountain card, put it onto the battlefield, then shuffle.

Falkenrath Pit Fighter

{1}{R}, Discard a card, Sacrifice a Vampire: Draw two cards. Activate only if an opponent lost life this turn.

Wish

You may play a card you own from outside the game this turn.

Underworld Breach

Each nonland card in your graveyard has escape. The escape cost is equal to the card's mana cost plus exile three other cards from your graveyard. (You may cast cards from your graveyard for their escape cost.)
At the beginning of the end step, sacrifice Underworld Breach.