Manabarbs

Whenever a player taps a land for mana, this enchantment deals 1 damage to that player.

Rakdos Signet

Raiders' Wake

Whenever an opponent discards a card, that player loses 2 life.
Raid — At the beginning of your end step, if you attacked this turn, target opponent discards a card.

Vial Smasher the Fierce

Whenever you cast your first spell each turn, choose an opponent at random. Vial Smasher deals damage equal to that spell's mana value to that player or a planeswalker that player controls.
Partner (You can have two commanders if both have partner.)

Kaervek the Merciless

Whenever an opponent casts a spell, Kaervek deals damage equal to that spell's mana value to any target.

Ob Nixilis of the Black Oath

+2: Each opponent loses 1 life. You gain life equal to the life lost this way.
−2: Create a 5/5 black Demon creature token with flying. You lose 2 life.
−8: You get an emblem with "{1}{B}, Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power."
Ob Nixilis of the Black Oath can be your commander.

Wound Reflection

At the beginning of each end step, each opponent loses life equal to the life they lost this turn. (Damage causes loss of life.)

Fellwar Stone

{T}: Add one mana of any color that a land an opponent controls could produce.

Court of Ambition

When this enchantment enters, you become the monarch.
At the beginning of your upkeep, each opponent loses 3 life unless they discard a card. If you're the monarch, instead each opponent loses 6 life unless they discard two cards.

Harsh Mentor

Whenever an opponent activates an ability of an artifact, creature, or land on the battlefield, if it isn't a mana ability, this creature deals 2 damage to that player.

Wayfarer's Bauble

{2}, {T}, Sacrifice this artifact: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Havoc Festival

Players can't gain life.
At the beginning of each player's upkeep, that player loses half their life, rounded up.

Barbflare Gremlin

First strike, haste
Whenever a player taps a land for mana, if this creature is tapped, that player adds one mana of any type that land produced. Then that land deals 1 damage to that player.

Torture Pit

If a source you control would deal noncombat damage to an opponent, it deals that much damage plus 2 instead.
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Spiked Corridor

When you unlock this door, create three 1/1 red Devil creature tokens with "When this token dies, it deals 1 damage to any target."
(You may cast either half. That door unlocks on the battlefield. As a sorcery, you may pay the mana cost of a locked door to unlock it.)

Spiked Corridor // Torture Pit

Mogis, God of Slaughter

Indestructible
As long as your devotion to black and red is less than seven, Mogis isn't a creature.
At the beginning of each opponent's upkeep, Mogis deals 2 damage to that player unless they sacrifice a creature of their choice.

Underworld Dreams

Whenever an opponent draws a card, this enchantment deals 1 damage to that player.

Kazuul, Tyrant of the Cliffs

Whenever a creature an opponent controls attacks, if you're the defending player, create a 3/3 red Ogre creature token unless that creature's controller pays {3}.

Spiteful Visions

At the beginning of each player's draw step, that player draws an additional card.
Whenever a player draws a card, this enchantment deals 1 damage to that player.

Blood Seeker

Whenever a creature an opponent controls enters, you may have that player lose 1 life.

Eidolon of the Great Revel

Whenever a player casts a spell with mana value 3 or less, this creature deals 2 damage to that player.

Chain Reaction

Chain Reaction deals X damage to each creature, where X is the number of creatures on the battlefield.

Ob Nixilis, the Adversary

Casualty X. The copy isn't legendary and has starting loyalty X. (As you cast this spell, you may sacrifice a creature with power X. When you do, copy this spell. The copy becomes a token.)
+1: Each opponent loses 2 life unless they discard a card. If you control a Demon or Devil, you gain 2 life.
−2: Create a 1/1 red Devil creature token with "When this token dies, it deals 1 damage to any target."
−7: Target player draws seven cards and loses 7 life.

Impact Tremors

Whenever a creature you control enters, this enchantment deals 1 damage to each opponent.

Fate Unraveler

Whenever an opponent draws a card, this creature deals 1 damage to that player.

Thran Dynamo

Leyline of Combustion

If this card is in your opening hand, you may begin the game with it on the battlefield.
Whenever you and/or at least one permanent you control becomes the target of a spell or ability an opponent controls, this enchantment deals 2 damage to that player.

Cunning Rhetoric

Whenever an opponent attacks you and/or one or more planeswalkers you control, exile the top card of that player's library. You may play that card for as long as it remains exiled, and you may spend mana as though it were mana of any color to cast it.

Mind Stone

{T}: Add {C}.
{1}, {T}, Sacrifice this artifact: Draw a card.

Polluted Bonds

Whenever a land an opponent controls enters, that player loses 2 life and you gain 2 life.

Spellshock

Whenever a player casts a spell, this enchantment deals 2 damage to that player.

Ob Nixilis, Unshackled

Flying, trample
Whenever an opponent searches their library, that player sacrifices a creature of their choice and loses 10 life.
Whenever another creature dies, put a +1/+1 counter on Ob Nixilis.

Outpost Siege

As this enchantment enters, choose Khans or Dragons.
• Khans — At the beginning of your upkeep, exile the top card of your library. Until end of turn, you may play that card.
• Dragons — Whenever a creature you control leaves the battlefield, this enchantment deals 1 damage to any target.

Solemn Simulacrum

When this creature enters, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When this creature dies, you may draw a card.

Gleeful Arsonist

Whenever an opponent casts a noncreature spell, this creature deals damage equal to its power to that player.
Undying (When this creature dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.)

Archfiend of Depravity

Flying
At the beginning of each opponent's end step, that player chooses up to two creatures they control, then sacrifices the rest.

Combustible Gearhulk

First strike
When this creature enters, target opponent may have you draw three cards. If the player doesn't, you mill three cards, then this creature deals damage to that player equal to the total mana value of those cards.

Terminate

Destroy target creature. It can't be regenerated.

Fear of Burning Alive

When this creature enters, it deals 4 damage to each opponent.
Delirium — Whenever a source you control deals noncombat damage to an opponent, if there are four or more card types among cards in your graveyard, this creature deals that amount of damage to target creature that player controls.

Marchesa's Decree

When this enchantment enters, you become the monarch.
Whenever a creature attacks you or a planeswalker you control, that creature's controller loses 1 life.

Go for the Throat

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Infernal Grasp

Destroy target creature. You lose 2 life.

Painful Quandary

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Vexing Devil

When this creature enters, any opponent may have it deal 4 damage to them. If a player does, sacrifice this creature.

Blasphemous Act

This spell costs {1} less to cast for each creature on the battlefield.
Blasphemous Act deals 13 damage to each creature.

Chaos Warp

The owner of target permanent shuffles it into their library, then reveals the top card of their library. If it's a permanent card, they put it onto the battlefield.

The Lord of Pain

Menace
Your opponents can't gain life.
Whenever a player casts their first spell each turn, choose another target player. The Lord of Pain deals damage equal to that spell's mana value to the chosen player.

Talisman of Indulgence

{T}: Add {C}.
{T}: Add {B} or {R}. This artifact deals 1 damage to you.

Roiling Vortex

At the beginning of each player's upkeep, this enchantment deals 1 damage to them.
Whenever a player casts a spell, if no mana was spent to cast that spell, this enchantment deals 5 damage to that player.
{R}: Your opponents can't gain life this turn.

Sin Prodder

Menace
At the beginning of your upkeep, reveal the top card of your library. Any opponent may have you put that card into your graveyard. If a player does, this creature deals damage to that player equal to that card's mana value. Otherwise, put that card into your hand.