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.

Reliquary Tower

You have no maximum hand size.
{T}: Add {C}.

Tempest Djinn

Flying
Tempest Djinn gets +1/+0 for each basic Island you control.

Aether Gust

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

Daniel

Master of Waves

Protection from red
Elemental creatures you control get +1/+1.
When Master of Waves enters the battlefield, 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.)

Deflection

Change the target of target spell with a single target.

Hibernation

Return all green permanents to their owners' hands.

Island

Douse

Siren's Call

Cast this spell only during an opponent's turn, before attackers are declared.
Creatures the active player controls attack this turn if able.
At the beginning of the next end step, destroy all non-Wall creatures that player controls that didn't attack this turn. Ignore this effect for each creature the player didn't control continuously since the beginning of the turn.

Abjure

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

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.)

Llawan, Cephalid Empress

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

Jodah's Avenger

{0}: Until end of turn, Jodah's Avenger gets -1/-1 and gains your choice of double strike, protection from red, vigilance, or shadow. (A creature with shadow can block or be blocked by only creatures with shadow.)

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.

High Tide

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

Ersatz Gnomes

{T}: Target spell becomes colorless.
{T}: Target permanent becomes colorless 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.

Treetop Sentinel

Withering Gaze

Target opponent reveals their hand. You draw a card for each Forest and green card in it.

Wrath of Marit Lage

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

Sisay's Ingenuity

Enchant creature
When Sisay's Ingenuity enters the battlefield, draw a card.
Enchanted creature has "{2}{U}: Target creature becomes the color of your choice until end of turn."

King Crab

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

Insight

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

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.)

Distorting Lens

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

Flow of Knowledge

Draw a card for each Island you control, then discard two cards.

Aven Smokeweaver

Sleight of Mind

Change the text of target spell or permanent by replacing all instances of one color word with another. (For example, you may change "target black spell" to "target blue spell." This effect lasts indefinitely.)

Caged Sun

As Caged Sun enters the battlefield, choose a color.
Creatures you control of the chosen color get +1/+1.
Whenever a land's ability causes you to add one or more mana of the chosen color, add one additional mana of that color.

Ceremonious Rejection

Mind Bend

Change the text of target permanent by replacing all instances of one color word with another or one basic land type with another. (For example, you may change "nonblack creature" to "nongreen creature" or "forestwalk" to "islandwalk." This effect lasts indefinitely.)

Vodalian Mystic

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

Chameleon Spirit

As Chameleon Spirit enters the battlefield, choose a color.
Chameleon Spirit's power and toughness are each equal to the number of permanents of the chosen color your opponents control.

Tidal Visionary

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

Blue Elemental Blast

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

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.

Sea Kings' Blessing

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

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.")

Homarid Shaman

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}.

Flash Flood

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

Inundate

Return all nonblue creatures to their owners' hands.

Shell Skulkin

{3}: Target blue creature gains shroud until end of turn. (It can't be the target of spells or abilities.)

Floodgate

Defender (This creature can't attack.)
When Floodgate has flying, sacrifice it.
When Floodgate leaves the battlefield, it deals damage equal to half the number of Islands you control, rounded down, to each nonblue creature without flying.

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.

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.)

Scuttlemutt

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

Ring of Evos Isle

{2}: Equipped creature gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
At the beginning of your upkeep, put a +1/+1 counter on equipped creature if it's blue.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Scourge of Fleets

When Scourge of Fleets enters the battlefield, return each creature your opponents control with toughness X or less to its owner's hand, where X is the number of Islands you control.

Essence Leak

Enchant permanent
As long as enchanted permanent is red or green, it has "At the beginning of your upkeep, sacrifice this permanent unless you pay its mana cost."

Govern the Guildless

Gain control of target monocolored creature.
Forecast — {1}{U}, Reveal Govern the Guildless from your hand: Target creature becomes the color or colors of your choice until end of turn. (Activate only during your upkeep and only once each turn.)

Blind Seer

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

Flashfreeze

Arcanis the Omnipotent

{T}: Draw three cards.
{2}{U}{U}: Return Arcanis the Omnipotent to its owner's hand.

Rhystic Study

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

Guile

Guile can't be blocked except by three or more creatures.
If a spell or ability you control would counter a spell, instead exile that spell and you may play that card without paying its mana cost.
When Guile is put into a graveyard from anywhere, shuffle it into its owner's library.

Quickchange

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

Riptide

Chill

Fylamarid

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

Lifetap

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

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.

Moonlace

Target spell or permanent becomes colorless.

Talrand, Sky Summoner

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

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.)

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}

Jaded Response

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

Hydroblast

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

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.

Baleful Stare

Target opponent reveals their hand. You draw a card for each Mountain and red card in it.

Wash Out

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

Shifting Sky

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

Cerulean Wyvern

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.

Sway of Illusion

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

Drain Power

Target player activates a mana ability of each land they control. Then that player loses all unspent mana and you add the mana lost this way.