Well-Laid Plans

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

Deepchannel Mentor

Blue creatures you control can't be blocked.

Barrin's Unmaking

Return target permanent to its owner's hand if that permanent shares a color with the most common color among all permanents or a color tied for most common.

King Crab

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

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.)

Coast Watcher

Sea Kings' Blessing

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

Swirl the Mists

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

Diamond Knight

Vigilance (Attacking doesn't cause this creature to tap.)
As Diamond Knight enters the battlefield, choose a color.
Whenever you cast a spell of the chosen color, put a +1/+1 counter on Diamond Knight.

Illuminated Folio

{1}, {T}, Reveal two cards from your hand that share a color: Draw a card.

Defiler of Dreams

Flying
As an additional cost to cast blue permanent spells, you may pay 2 life. Those spells cost {U} less to cast if you paid life this way. This effect reduces only the amount of blue mana you pay.
Whenever you cast a blue permanent spell, draw a card.

Cerulean Wisps

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

Prismwake Merrow

Flash
When Prismwake Merrow enters the battlefield, target permanent becomes the color or colors of your choice until end of turn.

Sanctuary Blade

As Sanctuary Blade becomes attached to a creature, choose a color.
Equipped creature gets +2/+0 and has protection from the last chosen color.
Equip {3}

Sway of Illusion

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

Inundate

Return all nonblue creatures to their owners' hands.

Alchor's Tomb

{2}, {T}: Target permanent you control becomes the color of your choice. (This effect lasts indefinitely.)

Vodalian Mystic

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

Cerulean Wyvern

Aven Smokeweaver

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.")

View from Above

Target creature gains flying until end of turn. If you control a white permanent, return View from Above to its owner's hand.

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.

Unexplained Vision

Draw three cards.
Adamant — If at least three blue mana was spent to cast this spell, scry 3.

Spectral Shift

Choose one —
• Change the text of target spell or permanent by replacing all instances of one basic land type with another. (This effect lasts indefinitely.)
• Change the text of target spell or permanent by replacing all instances of one color word with another. (This effect lasts indefinitely.)
Entwine {2} (Choose both if you pay the entwine cost.)

Faerie Swarm

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

Spell Syphon

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

Narwhal

Surge Mare

Surge Mare can't be blocked by green creatures.
Whenever Surge Mare deals damage to an opponent, you may draw a card. If you do, discard a card.
{1}{U}: Surge Mare gets +2/-2 until end of turn.

Ether Well

Put target creature on top of its owner's library. If that creature is red, you may put it on the bottom of its owner's library instead.

Treetop Sentinel

Konda's Banner

Konda's Banner can be attached only to a legendary creature.
Creatures that share a color with equipped creature get +1/+1.
Creatures that share a creature type with equipped creature get +1/+1.
Equip {2}

Jaded Response

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

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.)

Wingrattle Scarecrow

Wingrattle Scarecrow has flying as long as you control a blue creature.
Wingrattle Scarecrow has persist as long as you control a black creature. (When this creature 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.)

Kefnet's Monument

Blue creature spells you cast cost {1} less to cast.
Whenever you cast a creature spell, target creature an opponent controls doesn't untap during its controller's next untap step.

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.

Decanter of Endless Water

You have no maximum hand size.
{T}: Add one mana of any color.

Thassa's Rebuff

Counter target spell unless its controller pays {X}, where X is your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Manta Ray

Manta Ray can't attack unless defending player controls an Island.
Manta Ray can't be blocked except by blue creatures.
When you control no Islands, sacrifice Manta Ray.

Mourner's Shield

Imprint — When Mourner's Shield enters the battlefield, 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.

Prism Ring

As Prism Ring enters the battlefield, choose a color.
Whenever you cast a spell of the chosen color, you gain 1 life.

Heraldic Banner

As Heraldic Banner enters the battlefield, choose a color.
Creatures you control of the chosen color get +1/+0.
{T}: Add one mana of the chosen color.

Blind Seer

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

Fylamarid

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

Indigo Faerie

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

Quickchange

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

Crystal Spray

Change the text of target spell or permanent by replacing all instances of one color word with another or one basic land type with another until end of turn.
Draw a card.

Tidal Visionary

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

Metathran Transport

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

Weatherseed Faeries

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.

Island

Homarid Shaman

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.

Oraxid

Douse

Jawbone Skulkin

{2}: Target red creature gains haste until end of turn.

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.

Trait Doctoring

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.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Prismatic Lace

Target permanent becomes the color or colors of your choice. (This effect lasts indefinitely.)

Paragon of Gathering Mists

Other blue creatures you control get +1/+1.
{U}, {T}: Another target blue creature you control gains flying until end of turn.

The Phasing of Zhalfir

Read ahead (Choose a chapter and start with that many lore counters. Add one after your draw step. Skipped chapters don't trigger. Sacrifice after III.)
I, II — Another target nonland permanent phases out. It can't phase in for as long as you control The Phasing of Zhalfir.
III — Destroy all creatures. For each creature destroyed this way, its controller creates a 2/2 black Phyrexian creature token.