Sea of Clouds

Sea of Clouds enters tapped unless you have two or more opponents.
{T}: Add {W} or {U}.

Esper Sentinel

Whenever an opponent casts their first noncreature spell each turn, draw a card unless that player pays {X}, where X is Esper Sentinel's power.

Cleansing

For each land, destroy that land unless any player pays 1 life.

Training Center

Training Center enters tapped unless you have two or more opponents.
{T}: Add {U} or {R}.

Sivitri, Dragon Master

+1: Until your next turn, creatures can't attack you or planeswalkers you control unless their controller pays 2 life for each of those creatures.
−3: Search your library for a Dragon card, reveal it, put it into your hand, then shuffle.
−7: Destroy all non-Dragon creatures.
Sivitri, Dragon Master can be your commander.

Mirrodin's Core

{T}: Add {C}.
{T}: Put a charge counter on Mirrodin's Core.
{T}, Remove a charge counter from Mirrodin's Core: Add one mana of any color.

Erosion

Enchant land
At the beginning of the upkeep of enchanted land's controller, destroy that land unless that player pays {1} or 1 life.

Dimir Guildgate

Dimir Guildgate enters tapped.
{T}: Add {U} or {B}.

Scarwood Bandits

Forestwalk (This creature can't be blocked as long as defending player controls a Forest.)
{2}{G}, {T}: Unless an opponent pays {2}, gain control of target artifact for as long as Scarwood Bandits remains on the battlefield.

Savage Lands

Savage Lands enters tapped.
{T}: Add {B}, {R}, or {G}.

Sphere of Safety

Creatures can't attack you or planeswalkers you control unless their controller pays {X} for each of those creatures, where X is the number of enchantments you control.

Mystic Remora

Cumulative upkeep {1} (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.)
Whenever an opponent casts a noncreature spell, you may draw a card unless that player pays {4}.

Sandsteppe Citadel

Sandsteppe Citadel enters tapped.
{T}: Add {W}, {B}, or {G}.

Nazgûl Battle-Mace

Equipped creature has menace, deathtouch, annihilator 1, and "Whenever an opponent sacrifices a nontoken permanent, put that card onto the battlefield under your control unless that player pays 3 life." (Whenever a creature with annihilator 1 attacks, defending player sacrifices a permanent of their choice.)
Equip {3}

Archway Commons

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

Frontier Bivouac

Frontier Bivouac enters tapped.
{T}: Add {G}, {U}, or {R}.

Collective Restraint

Domain — Creatures can't attack you unless their controller pays {X} for each creature they control that's attacking you, where X is the number of basic land types among lands you control.

Archangel of Tithes

Flying
As long as Archangel of Tithes is untapped, creatures can't attack you or planeswalkers you control unless their controller pays {1} for each of those creatures.
As long as Archangel of Tithes is attacking, creatures can't block unless their controller pays {1} for each of those creatures.

Chancellor of the Annex

You may reveal this card from your opening hand. If you do, when each opponent casts their first spell of the game, counter that spell unless that player pays {1}.
Flying
Whenever an opponent casts a spell, counter it unless that player pays {1}.

Exotic Orchard

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

Gruul Guildgate

Gruul Guildgate enters tapped.
{T}: Add {R} or {G}.

Command Tower

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

Soul Barrier

Whenever an opponent casts a creature spell, Soul Barrier deals 2 damage to that player unless they pay {2}.

Boros Guildgate

Boros Guildgate enters tapped.
{T}: Add {R} or {W}.

Unsettled Mariner

Changeling (This card is every creature type.)
Whenever you or a permanent you control becomes the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays {1}.

Malignant Growth

Cumulative upkeep {1} (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.)
At the beginning of your upkeep, put a growth counter on Malignant Growth.
At the beginning of each opponent's draw step, that player draws an additional card for each growth counter on Malignant Growth, then Malignant Growth deals damage to the player equal to the number of cards they drew this way.

Shivan Reef

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

Pir's Whim

For each player, choose friend or foe. Each friend searches their library for a land card, puts it onto the battlefield tapped, then shuffles. Each foe sacrifices an artifact or enchantment of their choice.

Parnesse, the Subtle Brush

Whenever you or a permanent you control becomes the target of a spell or ability an opponent controls, counter that spell or ability unless that player pays 4 life.
Whenever you copy a spell, up to one target opponent may also copy that spell. They may choose new targets for that copy.

Rishadan Brigand

Flying
When Rishadan Brigand enters, each opponent sacrifices a permanent of their choice unless they pay {3}.
Rishadan Brigand can block only creatures with flying.

Sol Ring

Orzhov Guildgate

Orzhov Guildgate enters tapped.
{T}: Add {W} or {B}.

Izzet Guildgate

Izzet Guildgate enters tapped.
{T}: Add {U} or {R}.

Island

Aether Rift

At the beginning of your upkeep, discard a card at random. If you discard a creature card this way, return it from your graveyard to the battlefield unless any player pays 5 life.

Seizures

Enchant creature
Whenever enchanted creature becomes tapped, Seizures deals 3 damage to that creature's controller unless that player pays {3}.

Selesnya Guildgate

Selesnya Guildgate enters tapped.
{T}: Add {G} or {W}.

The Argent Etchings

(As this Saga enters and after your draw step, add a lore counter.)
I — Incubate 2 five times, then transform all Incubator tokens you control.
II — Creatures you control get +1/+1 and gain double strike until end of turn.
III — Destroy all other permanents except for artifacts, lands, and Phyrexians. Exile The Argent Etchings, then return it to the battlefield (front face up).

Elesh Norn

Vigilance
Whenever a source an opponent controls deals damage to you or a permanent you control, that source's controller loses 2 life unless they pay {1}.
{2}{W}, Sacrifice three other creatures: Exile Elesh Norn, then return it to the battlefield transformed under its owner's control. Activate only as a sorcery.

Elesh Norn // The Argent Etchings

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}.

Nomad Outpost

Nomad Outpost enters tapped.
{T}: Add {R}, {W}, or {B}.

Baird, Steward of Argive

Vigilance
Creatures can't attack you or planeswalkers you control unless their controller pays {1} for each of those creatures.

Champions of Minas Tirith

When Champions of Minas Tirith enters, you become the monarch.
At the beginning of combat on each opponent's turn, if you're the monarch, that opponent may pay {X}, where X is the number of cards in their hand. If they don't, they can't attack you this combat.

Simic Guildgate

Simic Guildgate enters tapped.
{T}: Add {G} or {U}.

Sivriss, Nightmare Speaker

{T}, Sacrifice another creature or an artifact: For each opponent, you mill a card, then return that card from your graveyard to your hand unless that player pays 3 life. (To mill a card, put the top card of your library into your graveyard.)
Choose a Background (You can have a Background as a second commander.)

Jungle Shrine

Jungle Shrine enters tapped.
{T}: Add {R}, {G}, or {W}.

Cascading Cataracts

Indestructible
{T}: Add {C}.
{5}, {T}: Add five mana in any combination of colors.

Strict Proctor

Flying
Whenever a permanent entering causes a triggered ability to trigger, counter that ability unless its controller pays {2}.

Path of Ancestry

Path of Ancestry enters 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.)

War's Toll

Whenever an opponent taps a land for mana, tap all lands that player controls.
If a creature an opponent controls attacks, all creatures that opponent controls attack if able.

Morphic Pool

Morphic Pool enters tapped unless you have two or more opponents.
{T}: Add {U} or {B}.

Golgari Guildgate

Golgari Guildgate enters tapped.
{T}: Add {B} or {G}.

Smothering Tithe

Whenever an opponent draws a card, that player may pay {2}. If the player doesn't, you create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Propaganda

Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Rishadan Footpad

When Rishadan Footpad enters, each opponent sacrifices a permanent of their choice unless they pay {2}.

Arcane Sanctum

Arcane Sanctum enters tapped.
{T}: Add {W}, {U}, or {B}.

Roaming Throne

Ward {2}
As Roaming Throne enters, choose a creature type.
Roaming Throne is the chosen type in addition to its other types.
If a triggered ability of another creature you control of the chosen type triggers, it triggers an additional time.

Opulent Palace

Opulent Palace enters tapped.
{T}: Add {B}, {G}, or {U}.

Windborn Muse

Flying
Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Arcane Signet

Nether Void

Whenever a player casts a spell, counter it unless that player pays {3}.

Transguild Promenade

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

Commander's Sphere

{T}: Add one mana of any color in your commander's color identity.
Sacrifice Commander's Sphere: Draw a card.

Athreos, God of Passage

Indestructible
As long as your devotion to white and black is less than seven, Athreos isn't a creature.
Whenever another creature you own dies, return it to your hand unless target opponent pays 3 life.

Luxury Suite

Luxury Suite enters tapped unless you have two or more opponents.
{T}: Add {B} or {R}.

Archon of Absolution

Flying
Protection from white (This creature can't be blocked, targeted, dealt damage, enchanted, or equipped by anything white.)
Creatures can't attack you or planeswalkers you control unless their controller pays {1} for each of those creatures.

Fellwar Stone

Tempt with Discovery

Tempting offer — Search your library for a land card and put it onto the battlefield. Each opponent may search their library for a land card and put it onto the battlefield. For each opponent who searches a library this way, search your library for a land card and put it onto the battlefield. Then each player who searched a library this way shuffles.

Seaside Citadel

Seaside Citadel enters tapped.
{T}: Add {G}, {W}, or {U}.

Brainwash

Enchant creature
Enchanted creature can't attack unless its controller pays {3}.

Essence Vortex

Destroy target creature unless its controller pays life equal to its toughness. A creature destroyed this way can't be regenerated.

Mana Tithe

Counter target spell unless its controller pays {1}.

Kyodai, Soul of Kamigawa

Flash
Flying
When Kyodai, Soul of Kamigawa enters, another target permanent gains indestructible for as long as you control Kyodai.
{W}{U}{B}{R}{G}: Kyodai gets +5/+5 until end of turn.

Ghostly Prison

Mystic Monastery

Mystic Monastery enters tapped.
{T}: Add {U}, {R}, or {W}.

Flusterstorm

Counter target instant or sorcery spell unless its controller pays {1}.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Maze's End

Maze's End enters tapped.
{T}: Add {C}.
{3}, {T}, Return Maze's End 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.

Underground River

{T}: Add {C}.
{T}: Add {U} or {B}. Underground River deals 1 damage to you.

Indulgent Tormentor

Flying
At the beginning of your upkeep, draw a card unless target opponent sacrifices a creature of their choice or pays 3 life.

In the Eye of Chaos

Whenever a player casts an instant spell, counter it unless that player pays {X}, where X is its mana value.

Koskun Falls

At the beginning of your upkeep, sacrifice Koskun Falls unless you tap an untapped creature you control.
Creatures can't attack you unless their controller pays {2} for each creature they control that's attacking you.

Battlefield Forge

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

Rakdos Guildgate

Rakdos Guildgate enters tapped.
{T}: Add {B} or {R}.

Spelltithe Enforcer

Whenever an opponent casts a spell, that player sacrifices a permanent of their choice unless they pay {1}.

Sedgemoor Witch

Menace
Ward—Pay 3 life. (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays 3 life.)
Magecraft — Whenever you cast or copy an instant or sorcery spell, create a 1/1 black and green Pest creature token with "When this creature dies, you gain 1 life."

Rupture Spire

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

Rishadan Cutpurse

When Rishadan Cutpurse enters, each opponent sacrifices a permanent of their choice unless they pay {1}.

Crumbling Necropolis

Crumbling Necropolis enters tapped.
{T}: Add {U}, {B}, or {R}.

Plains

Isolation Cell

Whenever an opponent casts a creature spell, that player loses 2 life unless they pay {2}.

Valkmira, Protector's Shield

If a source an opponent controls would deal damage to you or a permanent you control, prevent 1 of that damage.
Whenever you or another permanent you control becomes the target of a spell or ability an opponent controls, counter that spell or ability unless its controller pays {1}.

Reidane, God of the Worthy

Flying, vigilance
Snow lands your opponents control enter tapped.
Noncreature spells your opponents cast with mana value 4 or greater cost {2} more to cast.

Reidane, God of the Worthy // Valkmira, Protector's Shield

Protection Racket

At the beginning of your upkeep, repeat the following process for each opponent in turn order. Reveal the top card of your library. That player may pay life equal to that card's mana value. If they do, exile that card. Otherwise, put it into your hand.

Prince of Thralls

Whenever a permanent an opponent controls is put into a graveyard, put that card onto the battlefield under your control unless that opponent pays 3 life.

Energy Vortex

As Energy Vortex enters, choose an opponent.
At the beginning of your upkeep, remove all vortex counters from Energy Vortex.
At the beginning of the chosen player's upkeep, Energy Vortex deals 3 damage to that player unless they pay {1} for each vortex counter on Energy Vortex.
{X}: Put X vortex counters on Energy Vortex. Activate only during your upkeep.

Circuitous Route

Search your library for up to two basic land cards and/or Gate cards, put them onto the battlefield tapped, then shuffle.

Expedition Map

{2}, {T}, Sacrifice Expedition Map: Search your library for a land card, reveal it, put it into your hand, then shuffle.

Overencumbered

Enchant opponent
When Overencumbered enters, enchanted opponent creates a Clue token, a Food token, and a Junk token.
At the beginning of combat on enchanted opponent's turn, that player may pay {1} for each artifact they control. If they don't, creatures can't attack this combat.

Azorius Guildgate

Azorius Guildgate enters tapped.
{T}: Add {W} or {U}.

Norn's Annex

({W/P} can be paid with either {W} or 2 life.)
Creatures can't attack you or planeswalkers you control unless their controller pays {W/P} for each of those creatures.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Nils, Discipline Enforcer

At the beginning of your end step, for each player, put a +1/+1 counter on up to one target creature that player controls.
Each creature with one or more counters on it can't attack you or planeswalkers you control unless its controller pays {X}, where X is the number of counters on that creature.