The One Ring

Indestructible
When The One Ring enters the battlefield, if you cast it, you gain protection from everything until your next turn.
At the beginning of your upkeep, you lose 1 life for each burden counter on The One Ring.
{T}: Put a burden counter on The One Ring, then draw a card for each burden counter on The One Ring.

Mountain

Brine Elemental

Morph {5}{U}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)
When Brine Elemental is turned face up, each opponent skips their next untap step.

Fire Diamond

Fire Diamond enters the battlefield tapped.
{T}: Add {R}.

Empty City Ruse

Target opponent skips all combat phases of their next turn.

Rugged Prairie

{T}: Add {C}.
{R/W}, {T}: Add {R}{R}, {R}{W}, or {W}{W}.

Lyev Skyknight

Flying
When Lyev Skyknight enters the battlefield, detain target nonland permanent an opponent controls. (Until your next turn, that permanent can't attack or block and its activated abilities can't be activated.)

Take the Bait

Cast this spell only during an opponent's turn and only during combat.
Prevent all combat damage that would be dealt to you and planeswalkers you control this turn. Untap all attacking creatures and goad them. After this phase, there is an additional combat phase.

Fatespinner

At the beginning of each opponent's upkeep, that player chooses draw step, main phase, or combat phase. The player skips each instance of the chosen step or phase this turn.

Shivan Reef

{T}: Add {C}.
{T}: Add {U} or {R}. Shivan Reef deals 1 damage to you.

Temporal Manipulation

Sky Diamond

Sky Diamond enters the battlefield tapped.
{T}: Add {U}.

Grim Reaper's Sprint

Morbid — This spell costs {3} less to cast if a creature died this turn.
Enchant creature
When Grim Reaper's Sprint enters the battlefield, untap each creature you control. If it's your main phase, there is an additional combat phase after this phase.
Enchanted creature gets +2/+2 and has haste.

Command Tower

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

Stitch in Time

Flip a coin. If you win the flip, take an extra turn after this one.

Sigarda's Vanguard

Flash
Flying
Whenever Sigarda's Vanguard enters the battlefield or attacks, choose any number of creatures with different powers. Those creatures gain double strike until end of turn.

Reconnaissance

{0}: Remove target attacking creature you control from combat and untap it.

The Second Doctor

Players have no maximum hand size.
How Civil of You — At the beginning of your end step, each player may draw a card. Each opponent who does can't attack you or permanents you control during their next turn.

Medomai the Ageless

Flying
Whenever Medomai the Ageless deals combat damage to a player, take an extra turn after this one.
Medomai the Ageless can't attack during extra turns.

Talisman of Creativity

{T}: Add {C}.
{T}: Add {U} or {R}. Talisman of Creativity deals 1 damage to you.

Fractured Powerstone

{T}: Add {C}.
{T}: Roll the planar die. Activate only as a sorcery.

Boros Signet

New Prahv Guildmage

{W}{U}: Target creature gains flying until end of turn.
{3}{W}{U}: Detain target nonland permanent an opponent controls. (Until your next turn, that permanent can't attack or block and its activated abilities can't be activated.)

Lighthouse Chronologist

Level up {U} ({U}: Put a level counter on this. Level up only as a sorcery.)
LEVEL 4-6
2/4
LEVEL 7+
3/5
At the beginning of each end step, if it's not your turn, take an extra turn after this one.

Azorius Signet

Bloodthirster

Flying, trample
Whenever Bloodthirster deals combat damage to a player, untap it. After this combat phase, there is an additional combat phase.
Bloodthirster can't attack a player it has already attacked this turn.

Moment of Silence

Target player skips their next combat phase this turn.

Island

Sulfur Falls

Sulfur Falls enters the battlefield tapped unless you control an Island or a Mountain.
{T}: Add {U} or {R}.

Great Train Heist

Spree (Choose one or more additional costs.)
+ {2}{R} — Untap all creatures you control. If it's your combat phase, there is an additional combat phase after this phase.
+ {2} — Creatures you control get +1/+0 and gain first strike until end of turn.
+ {R} — Choose target opponent. Whenever a creature you control deals combat damage to that player this turn, create a tapped Treasure token.

Clifftop Retreat

Clifftop Retreat enters the battlefield tapped unless you control a Mountain or a Plains.
{T}: Add {R} or {W}.

Sundown Pass

Sundown Pass enters the battlefield tapped unless you control two or more other lands.
{T}: Add {R} or {W}.

Archon of the Triumvirate

Flying
Whenever Archon of the Triumvirate attacks, detain up to two target nonland permanents your opponents control. (Until your next turn, those permanents can't attack or block and their activated abilities can't be activated.)

Mystic Gate

{T}: Add {C}.
{W/U}, {T}: Add {W}{W}, {W}{U}, or {U}{U}.

Plains

Temporal Mastery

Take an extra turn after this one. Exile Temporal Mastery.
Miracle {1}{U} (You may cast this card for its miracle cost when you draw it if it's the first card you drew this turn.)

Stonehorn Dignitary

When Stonehorn Dignitary enters the battlefield, target opponent skips their next combat phase.

Illusionist's Gambit

Cast this spell only during the declare blockers step on an opponent's turn.
Remove all attacking creatures from combat and untap them. After this phase, there is an additional combat phase. Each of those creatures attacks that combat if able. They can't attack you or planeswalkers you control that combat.

Suppressor Skyguard

Flying
Whenever a player attacks you, if that player has another opponent who isn't being attacked, prevent all combat damage that would be dealt to you this combat.

Karlach, Fury of Avernus

Whenever you attack, if it's the first combat phase of the turn, untap all attacking creatures. They gain first strike until end of turn. After this phase, there is an additional combat phase.
Choose a Background (You can have a Background as a second commander.)

Glacial Fortress

Glacial Fortress enters the battlefield tapped unless you control a Plains or an Island.
{T}: Add {W} or {U}.

Adarkar Wastes

{T}: Add {C}.
{T}: Add {W} or {U}. Adarkar Wastes deals 1 damage to you.

Lavinia of the Tenth

Protection from red
When Lavinia of the Tenth enters the battlefield, detain each nonland permanent your opponents control with mana value 4 or less. (Until your next turn, those permanents can't attack or block and their activated abilities can't be activated.)

Odric, Lunarch Marshal

At the beginning of each combat, creatures you control gain first strike until end of turn if a creature you control has first strike. The same is true for flying, deathtouch, double strike, haste, hexproof, indestructible, lifelink, menace, reach, skulk, trample, and vigilance.

Silverblade Paladin

Soulbond (You may pair this creature with another unpaired creature when either enters the battlefield. They remain paired for as long as you control both of them.)
As long as Silverblade Paladin is paired with another creature, both creatures have double strike.

Port Razer

Whenever Port Razer deals combat damage to a player, untap each creature you control. After this phase, there is an additional combat phase.
Port Razer can't attack a player it has already attacked this turn.

Capture of Jingzhou

False Peace

Target player skips all combat phases of their next turn.

Seize the Day

Untap target creature. After this main phase, there is an additional combat phase followed by an additional main phase.
Flashback {2}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Aurelia, the Warleader

Flying, vigilance, haste
Whenever Aurelia, the Warleader attacks for the first time each turn, untap all creatures you control. After this phase, there is an additional combat phase.

Sacred Foundry

({T}: Add {R} or {W}.)
As Sacred Foundry enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

Steam Vents

({T}: Add {U} or {R}.)
As Steam Vents enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.

Moraug, Fury of Akoum

Each creature you control gets +1/+0 for each time it has attacked this turn.
Landfall — Whenever a land enters the battlefield under your control, if it's your main phase, there's an additional combat phase after this phase. At the beginning of that combat, untap all creatures you control.

Relentless Assault

Untap all creatures that attacked this turn. After this main phase, there is an additional combat phase followed by an additional main phase.

Éomer, Marshal of Rohan

Haste
Whenever one or more other attacking legendary creatures you control die, untap all creatures you control. After this phase, there is an additional combat phase. This ability triggers only once each turn.

Deserted Beach

Deserted Beach enters the battlefield tapped unless you control two or more other lands.
{T}: Add {W} or {U}.

Cascade Bluffs

{T}: Add {C}.
{U/R}, {T}: Add {U}{U}, {U}{R}, or {R}{R}.

Mangara, the Diplomat

Lifelink
Whenever an opponent attacks with creatures, if two or more of those creatures are attacking you and/or planeswalkers you control, draw a card.
Whenever an opponent casts their second spell each turn, draw a card.

Temporal Trespass

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Take an extra turn after this one. Exile Temporal Trespass.

Scourge of the Throne

Flying
Dethrone (Whenever this creature attacks the player with the most life or tied for most life, put a +1/+1 counter on it.)
Whenever Scourge of the Throne attacks for the first time each turn, if it's attacking the player with the most life or tied for most life, untap all attacking creatures. After this phase, there is an additional combat phase.

Izzet Signet

Path of Ancestry

Path of Ancestry enters the battlefield tapped.
{T}: Add one mana of any color in your commander's color identity. When that mana is spent to cast a creature spell that shares a creature type with your commander, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Hellkite Charger

Flying, haste
Whenever Hellkite Charger attacks, you may pay {5}{R}{R}. If you do, untap all attacking creatures and after this phase, there is an additional combat phase.

Stormcarved Coast

Stormcarved Coast enters the battlefield tapped unless you control two or more other lands.
{T}: Add {U} or {R}.

Talisman of Conviction

{T}: Add {C}.
{T}: Add {R} or {W}. Talisman of Conviction deals 1 damage to you.

Marble Diamond

Marble Diamond enters the battlefield tapped.
{T}: Add {W}.

Blinding Angel

Flying (This creature can't be blocked except by creatures with flying or reach.)
Whenever Blinding Angel deals combat damage to a player, that player skips their next combat phase.

Fatigue

Target player skips their next draw step.

Talisman of Progress

{T}: Add {C}.
{T}: Add {W} or {U}. Talisman of Progress deals 1 damage to you.

Combat Celebrant

If Combat Celebrant hasn't been exerted this turn, you may exert it as it attacks. When you do, untap all other creatures you control and after this phase, there is an additional combat phase. (An exerted creature won't untap during your next untap step.)

Savor the Moment

Take an extra turn after this one. Skip the untap step of that turn.

Théoden, King of Rohan

Whenever Théoden, King of Rohan or another Human enters the battlefield under your control, target creature gains double strike until end of turn.

Bruse Tarl, Boorish Herder

Whenever Bruse Tarl, Boorish Herder enters the battlefield or attacks, target creature you control gains double strike and lifelink until end of turn.
Partner (You can have two commanders if both have partner.)

Raugrin Triome

({T}: Add {U}, {R}, or {W}.)
Raugrin Triome enters the battlefield tapped.
Cycling {3} ({3}, Discard this card: Draw a card.)

True Conviction

Creatures you control have double strike and lifelink.

Eon Frolicker

Flying
When Eon Frolicker enters the battlefield, if you cast it, target opponent takes an extra turn after this one. Until your next turn, you and planeswalkers you control gain protection from that player. (You and planeswalkers you control can't be targeted, dealt damage, or enchanted by anything controlled by that player.)

Hexplate Wallbreaker

For Mirrodin! (When this Equipment enters the battlefield, create a 2/2 red Rebel creature token, then attach this to it.)
Equipped creature gets +2/+2.
Whenever equipped creature attacks, if it's the first combat phase of the turn, untap each attacking creature. After this phase, there is an additional combat phase.
Equip {3}{R}

Battlefield Forge

{T}: Add {C}.
{T}: Add {R} or {W}. Battlefield Forge deals 1 damage to you.

Aragorn, King of Gondor

Vigilance, lifelink
When Aragorn, King of Gondor enters the battlefield, you become the monarch.
Whenever Aragorn attacks, up to one target creature can't block this turn. If you're the monarch, creatures can't block this turn.

Aggravated Assault

{3}{R}{R}: Untap all creatures you control. After this main phase, there is an additional combat phase followed by an additional main phase. Activate only as a sorcery.

Shu Yun, the Silent Tempest

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Whenever you cast a noncreature spell, you may pay {R/W}{R/W}. If you do, target creature gains double strike until end of turn.

World at War

After the first postcombat main phase this turn, there's an additional combat phase followed by an additional main phase. At the beginning of that combat, untap all creatures that attacked this turn.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Arcane Signet

Yosei, the Morning Star

Flying
When Yosei, the Morning Star dies, target player skips their next untap step. Tap up to five target permanents that player controls.

Hallowed Fountain

({T}: Add {W} or {U}.)
As Hallowed Fountain enters the battlefield, you may pay 2 life. If you don't, it enters the battlefield tapped.