Brine Seer

{2}{U}, {T}: Reveal any number of blue cards in your hand. Counter target spell unless its controller pays {1} for each card revealed this way.

Filigree Fracture

Destroy target artifact or enchantment. If that permanent was blue or black, draw a card.

Display of Dominance

Choose one —
• Destroy target blue or black noncreature permanent.
• Permanents you control can't be the targets of blue or black spells your opponents control this turn.

Spell Syphon

Counter target spell unless its controller pays {1} for each blue permanent you control.

Riptide

Seek the Beast

Exile the top two cards of your library. Until your next end step, you may play those cards.

Questing Druid

Whenever you cast a spell that's white, blue, black, or red, put a +1/+1 counter on Questing Druid.

Questing Druid // Seek the Beast

Sword of Truth and Justice

Equipped creature gets +2/+2 and has protection from white and from blue.
Whenever equipped creature deals combat damage to a player, put a +1/+1 counter on a creature you control, then proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)
Equip {2}

Helm of the Ghastlord

Enchant creature
As long as enchanted creature is blue, it gets +1/+1 and has "Whenever this creature deals damage to an opponent, draw a card."
As long as enchanted creature is black, it gets +1/+1 and has "Whenever this creature deals damage to an opponent, that player discards a card."

Cerulean Wisps

Target creature becomes blue until end of turn. Untap that creature.
Draw a card.

Seedtime

Cast this spell only during your turn.
Take an extra turn after this one if an opponent cast a blue spell this turn.

Ricochet Trap

If an opponent cast a blue spell this turn, you may pay {R} rather than pay this spell's mana cost.
Change the target of target spell with a single target.

Painter's Servant

As Painter's Servant enters, choose a color.
All cards that aren't on the battlefield, spells, and permanents are the chosen color in addition to their other colors.

Conflux

Search your library for a white card, a blue card, a black card, a red card, and a green card. Reveal those cards, put them into your hand, then shuffle.

Fable of Wolf and Owl

Whenever you cast a green spell, you may create a 2/2 green Wolf creature token.
Whenever you cast a blue spell, you may create a 1/1 blue Bird creature token with flying.

Tiamat

Flying
When Tiamat enters, if you cast it, search your library for up to five Dragon cards not named Tiamat that each have different names, reveal them, put them into your hand, then shuffle.

Mindwrack Liege

Other blue creatures you control get +1/+1.
Other red creatures you control get +1/+1.
{U/R}{U/R}{U/R}{U/R}: You may put a blue or red creature card from your hand onto the battlefield.

Sea Kings' Blessing

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

Sunscape Familiar

Defender (This creature can't attack.)
Green spells and blue spells you cast cost {1} less to cast.

Magnetic Mountain

Blue creatures don't untap during their controllers' untap steps.
At the beginning of each player's upkeep, that player may choose any number of tapped blue creatures they control and pay {4} for each creature chosen this way. If the player does, untap those creatures.

Scion of Draco

Domain — This spell costs {2} less to cast for each basic land type among lands you control.
Flying
Each creature you control has vigilance if it's white, hexproof if it's blue, lifelink if it's black, first strike if it's red, and trample if it's green.

Burnout

Counter target instant spell if it's blue.
Draw a card at the beginning of the next turn's upkeep.

Reign of Chaos

Choose one —
• Destroy target Plains and target white creature.
• Destroy target Island and target blue creature.

Clout of the Dominus

Enchant creature
As long as enchanted creature is blue, it gets +1/+1 and has shroud. (It can't be the target of spells or abilities.)
As long as enchanted creature is red, it gets +1/+1 and has haste.

Dromar, the Banisher

Flying
Whenever Dromar, the Banisher deals combat damage to a player, you may pay {2}{U}. If you do, choose a color, then return all creatures of that color to their owners' hands.

Indigo Faerie

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

Autumn's Veil

Spells you control can't be countered by blue or black spells this turn, and creatures you control can't be the targets of blue or black spells this turn.

Darigaaz, the Igniter

Flying
Whenever Darigaaz, the Igniter deals combat damage to a player, you may pay {2}{R}. If you do, choose a color, then that player reveals their hand and Darigaaz deals damage to the player equal to the number of cards of that color revealed this way.

Abjure

As an additional cost to cast this spell, sacrifice a blue permanent.
Counter target spell.

Snapback

You may exile a blue card from your hand rather than pay this spell's mana cost.
Return target creature to its owner's hand.

Circle of Protection: Blue

{1}: The next time a blue source of your choice would deal damage to you this turn, prevent that damage.

Rith, the Awakener

Flying
Whenever Rith, the Awakener deals combat damage to a player, you may pay {2}{G}. If you do, choose a color, then create a 1/1 green Saproling creature token for each permanent of that color.

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.")

Witchstalker

Hexproof (This creature can't be the target of spells or abilities your opponents control.)
Whenever an opponent casts a blue or black spell during your turn, put a +1/+1 counter on Witchstalker.

Thistledown Liege

Flash
Other white creatures you control get +1/+1.
Other blue creatures you control get +1/+1.

Metathran Transport

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

Active Volcano

Choose one —
• Destroy target blue permanent.
• Return target Island to its owner's hand.

God-Pharaoh's Faithful

Whenever you cast a blue, black, or red spell, you gain 1 life.

Oversoul of Dusk

Protection from blue, from black, and from red

Cromat

{W}{B}: Destroy target creature blocking or blocked by Cromat.
{U}{R}: Cromat gains flying until end of turn.
{B}{G}: Regenerate Cromat.
{R}{W}: Cromat gets +1/+1 until end of turn.
{G}{U}: Put Cromat on top of its owner's library.

Flare of Denial

You may sacrifice a nontoken blue creature rather than pay this spell's mana cost.
Counter target spell.

Sword of Fire and Ice

Equipped creature gets +2/+2 and has protection from red and from blue.
Whenever equipped creature deals combat damage to a player, Sword of Fire and Ice deals 2 damage to any target and you draw a card.
Equip {2}

Faerie Swarm

Flying
Faerie Swarm's power and toughness are each equal to the number of blue permanents you control.

Rune of Protection: Blue

{W}: The next time a blue source of your choice would deal damage to you this turn, prevent that damage.
Cycling {2} ({2}, Discard this card: Draw a card.)

Bloated Toad

Protection from blue
Cycling {2} ({2}, Discard this card: Draw a card.)

Sword of Once and Future

Equipped creature gets +2/+2 and has protection from blue and from black.
Whenever equipped creature deals combat damage to a player, surveil 2. Then you may cast an instant or sorcery spell with mana value 2 or less from your graveyard without paying its mana cost. If that spell would be put into your graveyard, exile it instead.
Equip {2}

Steel of the Godhead

Enchant creature
As long as enchanted creature is white, it gets +1/+1 and has lifelink. (Damage dealt by the creature also causes its controller to gain that much life.)
As long as enchanted creature is blue, it gets +1/+1 and can't be blocked.

Treva, the Renewer

Flying
Whenever Treva, the Renewer deals combat damage to a player, you may pay {2}{W}. If you do, choose a color, then you gain 1 life for each permanent of that color.

Kraken's Eye

Whenever a player casts a blue spell, you may gain 1 life.

Disrupting Shoal

You may exile a blue card with mana value X from your hand rather than pay this spell's mana cost.
Counter target spell if its mana value is X.

Demon's Herald

{2}{B}, {T}, Sacrifice a blue creature, a black creature, and a red creature: Search your library for a card named Prince of Thralls, put it onto the battlefield, then shuffle.

Crosis, the Purger

Flying
Whenever Crosis, the Purger deals combat damage to a player, you may pay {2}{B}. If you do, choose a color, then that player reveals their hand and discards all cards of that color.

Fylamarid

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

Slippery Bogle

Hexproof (This creature can't be the target of spells or abilities your opponents control.)

Oona, Queen of the Fae

Flying
{X}{U/B}: Choose a color. Target opponent exiles the top X cards of their library. For each card of the chosen color exiled this way, create a 1/1 blue and black Faerie Rogue creature token with flying.

Thelon's Curse

Blue creatures don't untap during their controllers' untap steps.
At the beginning of each player's upkeep, that player may choose any number of tapped blue creatures they control and pay {U} for each creature chosen this way. If the player does, untap those creatures.

Pyroblast

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

Swirl the Mists

As Swirl the Mists enters, choose a color word.
All instances of color words in the text of spells and permanents are changed to the chosen color word.

Sphere of Reason

If a blue source would deal damage to you, prevent 2 of that damage.

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.

Crackleburr

{U/R}{U/R}, {T}, Tap two untapped red creatures you control: Crackleburr deals 3 damage to any target.
{U/R}{U/R}, {Q}, Untap two tapped blue creatures you control: Return target creature to its owner's hand. ({Q} is the untap symbol.)

Murkfiend Liege

Other green creatures you control get +1/+1.
Other blue creatures you control get +1/+1.
Untap all green and/or blue creatures you control during each other player's untap step.

Radiant Kavu

{R}{G}{W}: Prevent all combat damage blue creatures and black creatures would deal this turn.

Red Elemental Blast

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

Eyes of the Wisent

Whenever an opponent casts a blue spell during your turn, you may create a 4/4 green Elemental creature token.

Force of Negation

If it's not your turn, you may exile a blue card from your hand rather than pay this spell's mana cost.
Counter target noncreature spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Favor of the Overbeing

Enchant creature
As long as enchanted creature is green, it gets +1/+1 and has vigilance.
As long as enchanted creature is blue, it gets +1/+1 and has flying.

Force of Will

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.
Counter target spell.

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.)

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.