Barroom Brawl

Target creature you control fights target creature the opponent to your left controls. Then that player may copy this spell and may choose new targets for the copy.

Ruthless Predation

Target creature you control gets +1/+2 until end of turn. It fights target creature you don't control. (Each deals damage equal to its power to the other.)

Longstalk Brawl

Gift a tapped Fish (You may promise an opponent a gift as you cast this spell. If you do, they create a tapped 1/1 blue Fish creature token before its other effects.)
Choose target creature you control and target creature you don't control. Put a +1/+1 counter on the creature you control if the gift was promised. Then those creatures fight each other.

Ancient Animus

Put a +1/+1 counter on target creature you control if it's legendary. Then it fights target creature an opponent controls. (Each deals damage equal to its power to the other.)

Primal Might

Target creature you control gets +X/+X until end of turn. Then it fights up to one target creature you don't control.

Pounce

Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)

Legolas, Master Archer

Reach
Whenever you cast a spell that targets Legolas, Master Archer, put a +1/+1 counter on Legolas.
Whenever you cast a spell that targets a creature you don't control, Legolas deals damage equal to its power to up to one target creature.

Mutant's Prey

Target creature you control with a +1/+1 counter on it fights target creature an opponent controls. (Each deals damage equal to its power to the other.)

Tail Swipe

Choose target creature you control and target creature you don't control. If you cast this spell during your main phase, the creature you control gets +1/+1 until end of turn. Then those creatures fight each other. (Each deals damage equal to its power to the other.)

Titanic Brawl

This spell costs {1} less to cast if it targets a creature you control with a +1/+1 counter on it.
Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)

Malamet Battle Glyph

Choose target creature you control and target creature you don't control. If the creature you control entered this turn, put a +1/+1 counter on it. Then those creatures fight each other.

Prey Upon

Prizefight

Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)
Create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Savage Swipe

Target creature you control gets +2/+2 until end of turn if its power is 2. Then it fights target creature you don't control. (Each deals damage equal to its power to the other.)

Mage Duel

This spell costs {2} less to cast if you've cast another instant or sorcery spell this turn.
Target creature you control gets +1/+2 until end of turn. Then it fights target creature you don't control. (Each deals damage equal to its power to the other.)

Bushwhack

Choose one —
• Search your library for a basic land card, reveal it, put it into your hand, then shuffle.
• Target creature you control fights target creature you don't control. (Each deals damage equal to its power to the other.)