Deepchannel Mentor

Blue creatures you control can't be blocked.

Death Wind

Target creature gets -X/-X until end of turn.

Sky Diamond

Sol Talisman

Suspend 3—{1} (Rather than cast this card from your hand, pay {1} and exile it with three time counters on it. At the beginning of your upkeep, remove a time counter. When the last is removed, you may cast it without paying its mana cost.)
{T}: Add {C}{C}.

Spawning Kraken

Whenever a Kraken, Leviathan, Octopus, or Serpent you control deals combat damage to a player, create a 9/9 blue Kraken creature token.

Worn Powerstone

Worn Powerstone enters tapped.
{T}: Add {C}{C}.

Ponder

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

Nemesis of Reason

Whenever Nemesis of Reason attacks, defending player mills ten cards.

Thassa, God of the Sea

Indestructible
As long as your devotion to blue is less than five, Thassa isn't a creature. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)
At the beginning of your upkeep, scry 1.
{1}{U}: Target creature you control can't be blocked this turn.

Thryx, the Sudden Storm

Flash
Flying
Spells you cast with mana value 5 or greater cost {1} less to cast and can't be countered.

Snow-Covered Swamp

Archetype of Imagination

Creatures you control have flying.
Creatures your opponents control lose flying and can't have or gain flying.

Shipbreaker Kraken

{6}{U}{U}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)
When Shipbreaker Kraken becomes monstrous, tap up to four target creatures. Those creatures don't untap during their controllers' untap steps for as long as you control Shipbreaker Kraken.

Wonder

Flying
As long as Wonder is in your graveyard and you control an Island, creatures you control have flying.

Arcane Signet

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

Reliquary Tower

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

Temple of the False God

{T}: Add {C}{C}. Activate only if you control five or more lands.

Geistwave

Return target nonland permanent to its owner's hand. If you controlled that permanent, draw a card.

Dimir Signet

Wrexial, the Risen Deep

Islandwalk, swampwalk (This creature can't be blocked as long as defending player controls an Island or a Swamp.)
Whenever Wrexial, the Risen Deep deals combat damage to a player, you may cast target instant or sorcery card from that player's graveyard without paying its mana cost. If that spell would be put into a graveyard, exile it instead.

Kraken of the Straits

Creatures with power less than the number of Islands you control can't block Kraken of the Straits.

Icebreaker Kraken

This spell costs {1} less to cast for each snow land you control.
When Icebreaker Kraken enters, artifacts and creatures target opponent controls don't untap during that player's next untap step.
Return three snow lands you control to their owner's hand: Return Icebreaker Kraken to its owner's hand.

Mortuary Mire

Mortuary Mire enters tapped.
When Mortuary Mire enters, you may put target creature card from your graveyard on top of your library.
{T}: Add {B}.

Halimar Depths

Halimar Depths enters tapped.
When Halimar Depths enters, look at the top three cards of your library, then put them back in any order.
{T}: Add {U}.

Temple of Deceit

Temple of Deceit enters tapped.
When Temple of Deceit enters, scry 1.
{T}: Add {U} or {B}.

Feed the Swarm

Destroy target creature or enchantment an opponent controls. You lose life equal to that permanent's mana value.

Darkwater Catacombs

Sea-Dasher Octopus

Mutate {1}{U} (If you cast this spell for its mutate cost, put it over or under target non-Human creature you own. They mutate into the creature on top plus all abilities from under it.)
Flash
Whenever this creature deals combat damage to a player, draw a card.

Commander's Sphere

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

Serpent of Yawning Depths

Krakens, Leviathans, Octopuses, and Serpents you control can't be blocked except by Krakens, Leviathans, Octopuses, and Serpents.

Gilded Lotus

Slinn Voda, the Rising Deep

Kicker {1}{U} (You may pay an additional {1}{U} as you cast this spell.)
When Slinn Voda, the Rising Deep enters, if it was kicked, return all creatures to their owners' hands except for Merfolk, Krakens, Leviathans, Octopuses, and Serpents.

Quicksilver Amulet

{4}, {T}: You may put a creature card from your hand onto the battlefield.

Military Intelligence

Whenever you attack with two or more creatures, draw a card.

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.)

Exotic Orchard

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

Elder Deep-Fiend

Flash
Emerge {5}{U}{U} (You may cast this spell by sacrificing a creature and paying the emerge cost reduced by that creature's mana value.)
When you cast this spell, tap up to four target permanents.

Hullbreaker Horror

Flash
This spell can't be countered.
Whenever you cast a spell, choose up to one —
• Return target spell you don't control to its owner's hand.
• Return target nonland permanent to its owner's hand.

Fleet Swallower

Whenever Fleet Swallower attacks, target player mills half their library, rounded up.

Snow-Covered Island

Unmarked Grave

Search your library for a nonlegendary card, put that card into your graveyard, then shuffle.

Propaganda

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

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.

Octopus Umbra

Enchant creature
Enchanted creature has base power and toughness 8/8 and has "Whenever this creature attacks, you may tap target creature with power 8 or less."
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Wayfarer's Bauble

{2}, {T}, Sacrifice Wayfarer's Bauble: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Counterspell

Krothuss, Lord of the Deep

Flying
Whenever Krothuss, Lord of the Deep attacks, create a tapped and attacking token that's a copy of another target attacking creature. If that creature is a Kraken, Leviathan, Octopus, or Serpent, create two of those tokens instead.

Runo Stromkirk

Flying
When Runo Stromkirk enters, put up to one target creature card from your graveyard on top of your library.
At the beginning of your upkeep, look at the top card of your library. You may reveal that card. If a creature card with mana value 6 or greater is revealed this way, transform Runo Stromkirk.

Runo Stromkirk // Krothuss, Lord of the Deep

Junk Winder

Affinity for tokens (This spell costs {1} less to cast for each token you control.)
Whenever a token you control enters, tap target nonland permanent an opponent controls. It doesn't untap during its controller's next untap step.

Pongify

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

Bident of Thassa

Whenever a creature you control deals combat damage to a player, you may draw a card.
{1}{U}, {T}: Creatures your opponents control attack this turn if able.

Grim Harvest

Return target creature card from your graveyard to your hand.
Recover {2}{B} (When a creature is put into your graveyard from the battlefield, you may pay {2}{B}. If you do, return this card from your graveyard to your hand. Otherwise, exile this card.)

Charcoal Diamond

Charcoal Diamond enters tapped.
{T}: Add {B}.

Thought Vessel

Ice Tunnel

({T}: Add {U} or {B}.)
Ice Tunnel enters tapped.

Rush of Knowledge

Draw cards equal to the highest mana value among permanents you control.

Choked Estuary

As Choked Estuary enters, you may reveal an Island or Swamp card from your hand. If you don't, Choked Estuary enters tapped.
{T}: Add {U} or {B}.

Fellwar Stone

Crypt Incursion

Exile all creature cards from target player's graveyard. You gain 3 life for each card exiled this way.

Wormhole Serpent

{3}{U}: Target creature can't be blocked this turn.

Flow of Ideas

Inundate

Return all nonblue creatures to their owners' hands.

Buried Alive

Search your library for up to three creature cards, put them into your graveyard, then shuffle.

Command Tower

Rite of Replication

Kicker {5} (You may pay an additional {5} as you cast this spell.)
Create a token that's a copy of target creature. If this spell was kicked, create five of those tokens instead.

Quest for Ula's Temple

At the beginning of your upkeep, you may look at the top card of your library. If it's a creature card, you may reveal it and put a quest counter on Quest for Ula's Temple.
At the beginning of each end step, if there are three or more quest counters on Quest for Ula's Temple, you may put a Kraken, Leviathan, Octopus, or Serpent creature card from your hand onto the battlefield.

Thran Dynamo

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.)

Wizard Class

(Gain the next level as a sorcery to add its ability.)
You have no maximum hand size.
{2}{U}: Level 2
When this Class becomes level 2, draw two cards.
{4}{U}: Level 3
Whenever you draw a card, put a +1/+1 counter on target creature you control.

Whelming Wave

Return all creatures to their owners' hands except for Krakens, Leviathans, Octopuses, and Serpents.

Sol Ring

Night's Whisper

Kiora Bests the Sea God

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Create an 8/8 blue Kraken creature token with hexproof.
II — Tap all nonland permanents target opponent controls. They don't untap during their controller's next untap step.
III — Gain control of target permanent an opponent controls. Untap it.

Murder

Sunken Hollow

({T}: Add {U} or {B}.)
Sunken Hollow enters tapped unless you control two or more basic lands.

Brainstorm

Draw three cards, then put two cards from your hand on top of your library in any order.