Neheb, the Eternal

Afflict 3 (Whenever this creature becomes blocked, defending player loses 3 life.)
At the beginning of each of your postcombat main phases, add {R} for each 1 life your opponents have lost this turn.

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.)

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.

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.)

Jeska, Thrice Reborn

Jeska enters with a loyalty counter on her for each time you've cast a commander from the command zone this game.
0: Choose target creature. Until your next turn, if that creature would deal combat damage to one of your opponents, it deals triple that damage to that player instead.
−X: Jeska deals X damage to each of up to three targets.
Jeska, Thrice Reborn can be your commander.
Partner

Florian, Voldaren Scion

First strike
At the beginning of each of your postcombat main phases, look at the top X cards of your library, where X is the total amount of life your opponents lost this turn. Exile one of those cards and put the rest on the bottom of your library in a random order. You may play the exiled card this turn.

Talisman of Indulgence

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

Pyromancer's Goggles

{T}: Add {R}. When that mana is spent to cast a red instant or sorcery spell, copy that spell and you may choose new targets for the copy.

Burn at the Stake

As an additional cost to cast this spell, tap any number of untapped creatures you control.
Burn at the Stake deals damage to any target equal to three times the number of creatures tapped this way.

Fiery Emancipation

If a source you control would deal damage to a permanent or player, it deals triple that damage to that permanent or player instead.

Kederekt Parasite

Whenever an opponent draws a card, if you control a red permanent, you may have this creature deal 1 damage to that player.

Mind Stone

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

Mutinous Massacre

Choose odd or even. Destroy each creature with mana value of the chosen quality. Then gain control of all creatures until end of turn. Untap them. They gain haste until end of turn. (Zero is even.)

Obosh, the Preypiercer

Companion — Your starting deck contains only cards with odd mana values and land cards. (If this card is your chosen companion, you may put it into your hand from outside the game for {3} as a sorcery.)
If a source you control with an odd mana value would deal damage to a permanent or player, it deals double that damage to that permanent or player instead.

Isengard Unleashed

Damage can't be prevented this turn. If a source you control would deal damage this turn to an opponent or a permanent an opponent controls, it deals triple that damage instead.
Flashback {4}{R}{R}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Kaervek the Merciless

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

Scytheclaw Raptor

Whenever a player casts a spell, if it's not their turn, this creature deals 4 damage to them.

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.

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.

Stuffy Doll

Indestructible
As this creature enters, choose a player.
Whenever this creature is dealt damage, it deals that much damage to the chosen player.
{T}: This creature deals 1 damage to itself.

Zo-Zu the Punisher

Whenever a land enters, Zo-Zu deals 2 damage to that land's controller.

Sol Ring

Extinction Event

Choose odd or even. Exile each creature with mana value of the chosen quality. (Zero is even.)

Rankle and Torbran

Flying, first strike, haste
Whenever Rankle and Torbran deals combat damage to a player or battle, choose any number —
• Each player creates a Treasure token.
• Each player sacrifices a creature of their choice.
• If a source would deal damage to a player or battle this turn, it deals that much damage plus 2 instead.

Tor Wauki the Younger

Reach, lifelink
If another source you control would deal noncombat damage to a permanent or player, it deals that much damage plus 1 to that permanent or player instead.
Whenever you cast an instant or sorcery spell, Tor Wauki deals 2 damage to any target.

Rakdos Signet

Blisterspit Gremlin

{1}, {T}: This creature deals 1 damage to each opponent.
Whenever you cast a noncreature spell, untap this creature.

Brash Taunter

Indestructible
Whenever this creature is dealt damage, it deals that much damage to target opponent.
{2}{R}, {T}: This creature fights another target creature.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Torbran, Thane of Red Fell

If a red source you control would deal damage to an opponent or a permanent an opponent controls, it deals that much damage plus 2 instead.

Solphim, Mayhem Dominus

If a source you control would deal noncombat damage to an opponent or a permanent an opponent controls, it deals double that damage to that player or permanent instead.
{1}{R/P}{R/P}, Discard two cards: Put an indestructible counter on Solphim. ({R/P} can be paid with either {R} or 2 life.)

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.

Twins of Discord

Whenever you attack, choose odd or even. Creatures with mana value of that quality can't block this turn. (Zero is even.)
Each other colorless creature you control has bloodthirst 2. (If an opponent was dealt damage this turn, that creature enters with two additional +1/+1 counters on it.)

Angrath's Marauders

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

Drakuseth, Maw of Flames

Flying
Whenever Drakuseth attacks, it deals 4 damage to any target and 3 damage to each of up to two other targets.

Ashling's Prerogative

As this enchantment 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.

Ruby Medallion

Red spells you cast cost {1} less to cast.

Arcane Signet

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

Scab-Clan Berserker

Haste
Renown 1 (When this creature deals combat damage to a player, if it isn't renowned, put a +1/+1 counter on it and it becomes renowned.)
Whenever an opponent casts a noncreature spell, if this creature is renowned, this creature deals 2 damage to that player.

Heartless Hidetsugu

{T}: Heartless Hidetsugu deals damage to each player equal to half that player's life total, rounded down.