Blind Seer

{1}{U}: Target spell or permanent becomes the color of your choice until end of turn.

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Quickchange

Target creature becomes the color or colors of your choice until end of turn.
Draw a card.

Master of Waves

Protection from red
Elemental creatures you control get +1/+1.
When Master of Waves enters, create a number of 1/0 blue Elemental creature tokens equal to your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Hydroblast

Choose one —
• Counter target spell if it's red.
• Destroy target permanent if it's red.

High Seas

Red creature spells and green creature spells cost {1} more to cast.

Gainsay

Cowardice

Whenever a creature becomes the target of a spell or ability, return that creature to its owner's hand. (It won't be affected by the spell or ability.)

Negate

Archmage Emeritus

Magecraft — Whenever you cast or copy an instant or sorcery spell, draw a card.

Dismiss into Dream

Each creature your opponents control is an Illusion in addition to its other types and has "When this creature becomes the target of a spell or ability, sacrifice it."

Counterspell

Vodalian Mystic

{T}: Target instant or sorcery spell becomes the color of your choice.

Whim of Volrath

Buyback {2} (You may pay an additional {2} as you cast this spell. If you do, put this card into your hand as it resolves.)
Change the text of target permanent by replacing all instances of one color word with another or one basic land type with another until end of turn. (For example, you may change "nonred creature" to "nongreen creature" or "plainswalk" to "swampwalk.")

Tidebinder Mage

When Tidebinder Mage enters, tap target red or green creature an opponent controls. That creature doesn't untap during its controller's untap step for as long as you control Tidebinder Mage.

Sway of Illusion

Any number of target creatures become the color of your choice until end of turn.
Draw a card.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Tidal Control

Cumulative upkeep {2} (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.)
Pay 2 life or {2}: Counter target red or green spell. Any player may activate this ability.

Sea Sprite

Tidal Visionary

{T}: Target creature becomes the color of your choice until end of turn.

Homarid Shaman

Verity Circle

Whenever a creature an opponent controls becomes tapped, if it isn't being declared as an attacker, you may draw a card.
{4}{U}: Tap target creature without flying.

Llawan, Cephalid Empress

When Llawan, Cephalid Empress enters, return all blue creatures your opponents control to their owners' hands.
Your opponents can't cast blue creature spells.

Scuttlemutt

{T}: Add one mana of any color.
{T}: Target creature becomes the color or colors of your choice until end of turn.

Alter Reality

Change the text of target spell or permanent by replacing all instances of one color word with another. (This effect lasts indefinitely.)
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Capsize

Buyback {3} (You may pay an additional {3} as you cast this spell. If you do, put this card into your hand as it resolves.)
Return target permanent to its owner's hand.

Wash Out

Return all permanents of the color of your choice to their owners' hands.

Flashfreeze

Glamerdye

Change the text of target spell or permanent by replacing all instances of one color word with another.
Retrace (You may cast this card from your graveyard by discarding a land card in addition to paying its other costs.)

Insight

Whenever an opponent casts a green spell, you draw a card.

Shifting Sky

As Shifting Sky enters, choose a color.
All nonland permanents are the chosen color.

Sea Kings' Blessing

One or more target creatures become blue until end of turn.

Aether Gust

Choose target spell or permanent that's red or green. Its owner puts it on the top or bottom of their library.

Distorting Lens

{T}: Target permanent becomes the color of your choice until end of turn.

Orvar, the All-Form

Changeling
Whenever you cast an instant or sorcery spell, if it targets one or more other permanents you control, create a token that's a copy of one of those permanents.
When a spell or ability an opponent controls causes you to discard this card, create a token that's a copy of target permanent.

Commander's Plate

Equipped creature gets +3/+3 and has protection from each color that's not in your commander's color identity.
Equip commander {3}
Equip {5}

Heartstone

Activated abilities of creatures cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Sapphire Medallion

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

Mourner's Shield

Imprint — When Mourner's Shield enters, you may exile target card from a graveyard.
{2}, {T}: Prevent all damage that would be dealt this turn by a source of your choice that shares a color with the exiled card.

Metathran Transport

Flying
Metathran Transport can't be blocked by blue creatures.
{U}: Target creature becomes blue until end of turn.

Ravenform

Exile target artifact or creature. Its controller creates a 1/1 blue Bird creature token with flying.
Foretell {U} (During your turn, you may pay {2} and exile this card from your hand face down. Cast it on a later turn for its foretell cost.)

Sword of Hearth and Home

Equipped creature gets +2/+2 and has protection from green and from white.
Whenever equipped creature deals combat damage to a player, exile up to one target creature you own, then search your library for a basic land card. Put both cards onto the battlefield under your control, then shuffle.
Equip {2}

Lifetap

Whenever a Forest an opponent controls becomes tapped, you gain 1 life.

Willbreaker

Whenever a creature an opponent controls becomes the target of a spell or ability you control, gain control of that creature for as long as you control Willbreaker.

Douse

Consign to Dream

Return target permanent to its owner's hand. If that permanent is red or green, put it on top of its owner's library instead.

Fylamarid

Flying
Fylamarid can't be blocked by blue creatures.
{U}: Target creature becomes blue until end of turn.

Stormtide Leviathan

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
All lands are Islands in addition to their other types.
Creatures without flying or islandwalk can't attack.

Indigo Faerie

Flying
{U}: Target permanent becomes blue in addition to its other colors until end of turn.

Well-Laid Plans

Prevent all damage that would be dealt to a creature by another creature if they share a color.

Wrath of Marit Lage

When Wrath of Marit Lage enters, tap all red creatures.
Red creatures don't untap during their controllers' untap steps.

King Crab

{1}{U}, {T}: Put target green creature on top of its owner's library.

Archaeomancer

When Archaeomancer enters, return target instant or sorcery card from your graveyard to your hand.

Reality Shift

Exile target creature. Its controller manifests the top card of their library. (That player puts the top card of their library onto the battlefield face down as a 2/2 creature. If it's a creature card, it can be turned face up any time for its mana cost.)

Hibernation

Return all green permanents to their owners' hands.

Flash Flood

Choose one —
• Destroy target red permanent.
• Return target Mountain to its owner's hand.

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Jaded Response

Counter target spell if it shares a color with a creature you control.

Talrand, Sky Summoner

Whenever you cast an instant or sorcery spell, create a 2/2 blue Drake creature token with flying.

Reconnaissance Mission

Whenever a creature you control deals combat damage to a player, you may draw a card.
Cycling {2} ({2}, Discard this card: Draw a card.)

Mind Harness

Enchant red or green creature
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.)
You control enchanted creature.

Arcane Signet

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

Grand Architect

Other blue creatures you control get +1/+1.
{U}: Target artifact creature becomes blue until end of turn.
Tap an untapped blue creature you control: Add {C}{C}. Spend this mana only to cast artifact spells or activate abilities of artifacts.

Coast Watcher

Inundate

Return all nonblue creatures to their owners' hands.

Cerulean Drake

Flying
Protection from red (This creature can't be blocked, targeted, dealt damage, enchanted, or equipped by anything red.)
Sacrifice Cerulean Drake: Counter target spell that targets you.