Antagonism

At the beginning of each player's end step, Antagonism deals 2 damage to that player unless one of their opponents was dealt damage this turn.

Caverns of Despair

No more than two creatures can attack each combat.
No more than two creatures can block each combat.

Burning Sands

Whenever a creature dies, that creature's controller sacrifices a land.

Blood Moon

Blood Mist

At the beginning of combat on your turn, target creature you control gains double strike until end of turn.

Dictate of the Twin Gods

Flash
If a source would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Tempered in Solitude

Whenever a creature you control attacks alone, exile the top card of your library. You may play that card this turn.

City on Fire

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
If a source you control would deal damage to a permanent or player, it deals triple that damage instead.

Citadel of Pain

At the beginning of each player's end step, Citadel of Pain deals X damage to that player, where X is the number of untapped lands they control.

Ashling's Prerogative

As Ashling's Prerogative enters, choose odd or even. (Zero is even.)
Each creature with mana value of the chosen quality has haste.
Each creature without mana value of the chosen quality enters tapped.

Ancient Runes

At the beginning of each player's upkeep, Ancient Runes deals damage to that player equal to the number of artifacts they control.

Aether Sting

Whenever an opponent casts a creature spell, Aether Sting deals 1 damage to that player.

Guild Artisan

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, you create two Treasure tokens." (They're artifacts with "{T}, Sacrifice this artifact: Add one mana of any color.")

Aether Flash

Whenever a creature enters, Aether Flash deals 2 damage to it.

Circle of Flame

Whenever a creature without flying attacks you or a planeswalker you control, Circle of Flame deals 1 damage to that creature.

Close Quarters

Whenever a creature you control becomes blocked, Close Quarters deals 1 damage to any target.

Battle Plan

At the beginning of combat on your turn, target creature you control gets +2/+0 until end of turn.
Basic landcycling {1}{R} ({1}{R}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Smoke

Players can't untap more than one creature during their untap steps.

Tavern Brawler

Commander creatures you own have "At the beginning of your upkeep, exile the top card of your library. This creature gets +X/+0 until end of turn, where X is that card's mana value. You may play that card this turn."

Braid of Fire

Cumulative upkeep—Add {R}. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

Burning Earth

Whenever a player taps a nonbasic land for mana, Burning Earth deals 1 damage to that player.

Berserkers' Onslaught

Attacking creatures you control have double strike.

Hazoret the Fervent

Indestructible, haste
Hazoret the Fervent can't attack or block unless you have one or fewer cards in hand.
{2}{R}, Discard a card: Hazoret deals 2 damage to each opponent.

Battle Strain

Whenever a creature blocks, Battle Strain deals 1 damage to that creature's controller.