Mirri, Weatherlight Duelist

First strike
Whenever Mirri attacks, each opponent can't block with more than one creature this combat.
As long as Mirri is tapped, no more than one creature can attack you each combat.

Mimeoplasm, Revered One

As Mimeoplasm enters, exile up to X creature cards from your graveyard. It enters with three +1/+1 counters on it for each creature card exiled this way.
{2}: Mimeoplasm becomes a copy of target creature card exiled with it, except it's 0/0 and has this ability.

Exotic Orchard

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

Urgoros, the Empty One

Flying
Whenever Urgoros deals combat damage to a player, that player discards a card at random. If the player can't, you draw a card.

One Dozen Eyes

Choose one —
• Create a 5/5 green Beast creature token.
• Create five 1/1 green Insect creature tokens.
Entwine {G}{G}{G} (Choose both if you pay the entwine cost.)

Snow-Covered Forest

Heedless One

Trample
Heedless One's power and toughness are each equal to the number of Elves on the battlefield.

Guan Yu's 1,000-Li March

Judoon Enforcers

Trample
No more than one creature can attack you each combat.
Suspend 6—{1}{R}{W} (Rather than cast this card from your hand, you may pay {1}{R}{W} and exile it with six time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost. It has haste.)

Manor Gate

This land enters tapped.
As this land enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

One Last Job

Spree (Choose one or more additional costs.)
+ {2} — Return target creature card from your graveyard to the battlefield.
+ {1} — Return target Mount or Vehicle card from your graveyard to the battlefield.
+ {1} — Return target Aura or Equipment card from your graveyard to the battlefield attached to a creature you control.

One Ring to Rule Them All

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — The Ring tempts you, then each player mills cards equal to your Ring-bearer's power.
II — Destroy all nonlegendary creatures.
III — Each opponent loses 1 life for each creature card in that player's graveyard.

Cyclops of One-Eyed Pass

Glowing One

Deathtouch
Whenever this creature deals combat damage to a player, they get four rad counters.
Whenever a player mills a nonland card, you gain 1 life.

Fight as One

Choose one or both —
• Target Human creature you control gets +1/+1 and gains indestructible until end of turn.
• Target non-Human creature you control gets +1/+1 and gains indestructible until end of turn.

Black Dragon Gate

This land enters tapped.
As this land enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

One-Eyed Scarecrow

Defender
Creatures with flying your opponents control get -1/-0.

Snow-Covered Plains

Haunted One

Commander creatures you own have "Whenever this creature becomes tapped, it and other creatures you control that share a creature type with it each get +2/+0 and gain undying until end of turn." (When a creature with undying 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.)

Thriving Isle

This land enters tapped. As it enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

Wall of One Thousand Cuts

Defender, flying
{W}: This creature can attack this turn as though it didn't have defender.

Origin of the Hidden Ones

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — This Saga deals 4 damage to any target.
II — Create two 1/1 black Assassin creature tokens with menace.
III — Whenever an Assassin you control attacks this turn, create a 1/1 black Assassin creature token with menace that's tapped and attacking.

One of the Pack

At the beginning of each upkeep, if a player cast two or more spells last turn, transform this creature.

Solitary Hunter

At the beginning of each upkeep, if no spells were cast last turn, transform this creature.

Solitary Hunter // One of the Pack

Command Tower

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

Reckless One

Haste
Reckless One's power and toughness are each equal to the number of Goblins on the battlefield.

Lightning, Army of One

First strike, trample, lifelink
Stagger — Whenever Lightning deals combat damage to a player, until your next turn, if a source would deal damage to that player or a permanent that player controls, it deals double that damage instead.

Soulless One

Soulless One's power and toughness are each equal to the number of Zombies on the battlefield plus the number of Zombie cards in all graveyards.

One with the Multiverse

You may look at the top card of your library any time.
You may play lands and cast spells from the top of your library.
Once during each of your turns, you may cast a spell from your hand or the top of your library without paying its mana cost.

Doubtless One

Doubtless One's power and toughness are each equal to the number of Clerics on the battlefield.
Whenever this creature deals damage, you gain that much life.

Unforgiving One

Menace (This creature can't be blocked except by two or more creatures.)
Whenever this creature attacks, return target creature card with mana value X or less from your graveyard to the battlefield, where X is the number of modified creatures you control. (Equipment, Auras you control, and counters are modifications.)

Sea Gate

This land enters tapped.
As this land enters, choose a color other than blue.
{T}: Add {U} or one mana of the chosen color.

The One Ring

Indestructible
When The One Ring enters, 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.

HELIOS One

{T}: Add {C}.
{1}, {T}: You get {E} (an energy counter).
{3}, {T}, Pay X {E}, Sacrifice this land: Destroy target nonland permanent with mana value X. Activate only as a sorcery.

Forbidden Orchard

{T}: Add one mana of any color.
Whenever you tap this land for mana, target opponent creates a 1/1 colorless Spirit creature token.

Iname as One

When Iname as One enters, if you cast it from your hand, you may search your library for a Spirit permanent card, put it onto the battlefield, then shuffle.
When Iname as One dies, you may exile it. If you do, return target Spirit permanent card from your graveyard to the battlefield.

Hollow One

This spell costs {2} less to cast for each card you've cycled or discarded this turn.
Cycling {2} ({2}, Discard this card: Draw a card.)

One with the Machine

Draw cards equal to the greatest mana value among artifacts you control.

Xiahou Dun, the One-Eyed

Horsemanship (This creature can't be blocked except by creatures with horsemanship.)
Sacrifice Xiahou Dun: Return target black card from your graveyard to your hand. Activate only during your turn, before attackers are declared.

Single Combat

Each player chooses a creature or planeswalker they control, then sacrifices the rest. Players can't cast creature or planeswalker spells until the end of your next turn.

Hero of Precinct One

Whenever you cast a multicolored spell, create a 1/1 white Human creature token.

Of One Mind

This spell costs {2} less to cast if you control a Human creature and a non-Human creature.
Draw two cards.

Rapacious One

Trample
Whenever this creature deals combat damage to a player, create that many 0/1 colorless Eldrazi Spawn creature tokens. They have "Sacrifice this token: Add {C}."

Thriving Heath

This land enters tapped. As it enters, choose a color other than white.
{T}: Add {W} or one mana of the chosen color.

Gateway Plaza

This land enters tapped.
When this land enters, sacrifice it unless you pay {1}.
{T}: Add one mana of any color.

Isshin, Two Heavens as One

If a creature attacking causes a triggered ability of a permanent you control to trigger, that ability triggers an additional time.

Heap Gate

{T}: Add {C}.
{1}, {T}: Add one mana of any color.
{1}, {T}, Tap an untapped Gate you control: Create a Treasure token. (It's an artifact with "{T}, Sacrifice this token: Add one mana of any color.")

Last One Standing

Choose a creature at random, then destroy the rest.

Sephiroth, One-Winged Angel

Flying
Super Nova — As this creature transforms into Sephiroth, One-Winged Angel, you get an emblem with "Whenever a creature dies, target opponent loses 1 life and you gain 1 life."
Whenever Sephiroth attacks, you may sacrifice any number of other creatures. If you do, draw that many cards.

Sephiroth, Fabled SOLDIER

Whenever Sephiroth enters or attacks, you may sacrifice another creature. If you do, draw a card.
Whenever another creature dies, target opponent loses 1 life and you gain 1 life. If this is the fourth time this ability has resolved this turn, transform Sephiroth.

Sephiroth, Fabled SOLDIER // Sephiroth, One-Winged Angel

Snow-Covered Mountain

Thriving Bluff

This land enters tapped. As it enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

Uncharted Haven

This land enters tapped. As it enters, choose a color.
{T}: Add one mana of the chosen color.

Silent Arbiter

No more than one creature can attack each combat.
No more than one creature can block each combat.

One With the Wind

Enchant creature
Enchanted creature gets +2/+2 and has flying.

Faceless One

If Faceless One is your commander, choose a color before the game begins. Faceless One is the chosen color.
Choose a Background (You can have a Background as a second commander.)

All Will Be One

Whenever you put one or more counters on a permanent or player, this enchantment deals that much damage to target opponent, creature an opponent controls, or planeswalker an opponent controls.

Garth One-Eye

{T}: Choose a card name that hasn't been chosen from among Disenchant, Braingeyser, Terror, Shivan Dragon, Regrowth, and Black Lotus. Create a copy of the card with the chosen name. You may cast the copy. (You still pay its costs.)

One-Clown Band

{2}{R}: Target Robot gets +2/+0 until end of turn.

Dueling Grounds

The Eternal Wanderer

No more than one creature can attack The Eternal Wanderer each combat.
+1: Exile up to one target artifact or creature. Return that card to the battlefield under its owner's control at the beginning of that player's next end step.
0: Create a 2/2 white Samurai creature token with double strike.
−4: For each player, choose a creature that player controls. Each player sacrifices all creatures they control not chosen this way.

Thriving Grove

This land enters tapped. As it enters, choose a color other than green.
{T}: Add {G} or one mana of the chosen color.

Joo Dee, One of Many

{B}, {T}: Surveil 1. Create a token that's a copy of this creature, then sacrifice an artifact or creature. Activate only as a sorcery. (To surveil 1, look at the top card of your library. You may put it into your graveyard.)

Plaza of Heroes

{T}: Add {C}.
{T}: Add one mana of any color. Spend this mana only to cast a legendary spell.
{T}: Add one mana of any color among legendary permanents you control.
{3}, {T}, Exile this land: Target legendary creature gains hexproof and indestructible until end of turn.

Snow-Covered Swamp

Endless One

This creature enters with X +1/+1 counters on it.

Snow-Covered Island

No One Left Behind

This spell costs {3} less to cast if it targets a creature card with mana value 3 or less.
Return target creature card from your graveyard to the battlefield.

Mana Confluence

{T}, Pay 1 life: Add one mana of any color.

Reflecting Pool

{T}: Add one mana of any type that a land you control could produce.

Citadel Gate

This land enters tapped.
As this land enters, choose a color other than white.
{T}: Add {W} or one mana of the chosen color.

Nameless One

Nameless One's power and toughness are each equal to the number of Wizards on the battlefield.
Morph {2}{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.)

Experiment One

Evolve (Whenever a creature you control enters, if that creature has greater power or toughness than this creature, put a +1/+1 counter on this creature.)
Remove two +1/+1 counters from this creature: Regenerate it. (The next time this creature would be destroyed this turn, instead tap it, remove it from combat, and heal all damage on it.)

Flayed One

Lifelink
Flesh Flayer — When this creature enters, mill three cards.

It That Rides as One

Lone Rider

First strike, lifelink
At the beginning of the end step, if you gained 3 or more life this turn, transform this creature.

Lone Rider // It That Rides as One

City of Brass

Whenever this land becomes tapped, it deals 1 damage to you.
{T}: Add one mana of any color.

Jon Irenicus, Shattered One

At the beginning of your end step, target opponent gains control of up to one target creature you control. Put two +1/+1 counters on it and tap it. It's goaded for the rest of the game and it gains "This creature can't be sacrificed." (It attacks each combat if able and attacks a player other than you if able.)
Whenever a creature you own but don't control attacks, you draw a card.

Cliffgate

This land enters tapped.
As this land enters, choose a color other than red.
{T}: Add {R} or one mana of the chosen color.

One with the Stars

Enchant creature or enchantment
Enchanted permanent is an enchantment and loses all other card types. (It still has its abilities, but it's no longer a creature.)

Gond Gate

Gates you control enter untapped.
{T}: Add {C}.
{T}: Add one mana of any color that a Gate you control could produce.

Opal Palace

{T}: Add {C}.
{1}, {T}: Add one mana of any color in your commander's color identity. If you spend this mana to cast your commander, it enters with a number of additional +1/+1 counters on it equal to the number of times it's been cast from the command zone this game.

Wandering Ones

Thriving Moor

This land enters tapped. As it enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

One with Nothing

Valgavoth's Lair

Hexproof
This land enters tapped. As it enters, choose a color.
{T}: Add one mana of the chosen color.

One with the Kami

Flash
Enchant creature you control
Whenever enchanted creature or another modified creature you control dies, create X 1/1 colorless Spirit creature tokens, where X is that creature's power. (Equipment, Auras you control, and counters are modifications.)

Hundred-Handed One

Vigilance
{3}{W}{W}{W}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
As long as this creature is monstrous, it has reach and can block an additional ninety-nine creatures each combat.

One Thousand Lashes

Enchant creature
Enchanted creature can't attack or block, and its activated abilities can't be activated.
At the beginning of the upkeep of enchanted creature's controller, that player loses 1 life.

One with Nature

Enchant creature
Whenever enchanted creature deals combat damage to a player, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Baldur's Gate

{T}: Add {C}.
{2}, {T}: Add X mana of any one color, where X is the number of other Gates you control.

Old One Eye

Trample
Other creatures you control have trample.
When Old One Eye enters, create a 5/5 green Tyranid creature token.
Fast Healing — At the beginning of your first main phase, you may discard two cards. If you do, return this card from your graveyard to your hand.

Mishra, Eminent One

At the beginning of combat on your turn, create a token that's a copy of target noncreature artifact you control, except its name is Mishra's Warform and it's a 4/4 Construct artifact creature in addition to its other types. It gains haste until end of turn. Sacrifice it at the beginning of the next end step.

Sheoldred, Whispering One

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
At the beginning of your upkeep, return target creature card from your graveyard to the battlefield.
At the beginning of each opponent's upkeep, that player sacrifices a creature of their choice.

The Ancient One

Descend 8 — The Ancient One can't attack or block unless there are eight or more permanent cards in your graveyard.
{2}{U}{B}: Draw a card, then discard a card. When you discard a card this way, target player mills cards equal to its mana value.

Gahiji, Honored One

Whenever a creature attacks one of your opponents or a planeswalker an opponent controls, that creature gets +2/+0 until end of turn.

Great Unclean One

Reverberating Summons — At the beginning of your end step, each opponent loses 2 life. Then for each opponent who has less life than you, create a 1/3 black Demon creature token named Plaguebearer of Nurgle.

Maze's End

This land enters tapped.
{T}: Add {C}.
{3}, {T}, Return this land to its owner's hand: Search your library for a Gate card, put it onto the battlefield, then shuffle. If you control ten or more Gates with different names, you win the game.