Foul Watcher

Flying
When this creature enters, surveil 1. (Look at the top card of your library. You may put that card into your graveyard.)
Delirium — This creature gets +1/+0 as long as there are four or more card types among cards in your graveyard.

High Tide

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

Slipstream Serpent

This creature can't attack unless defending player controls an Island.
When you control no Islands, sacrifice this creature.
Morph {5}{U} (You may cast this card face down as a 2/2 creature for {3}. Turn it face up any time for its morph cost.)

Whirlpool Whelm

Clash with an opponent, then return target creature to its owner's hand. If you win, you may put that creature on top of its owner's library instead. (Each clashing player reveals the top card of their library, then puts that card on their choice of the top or bottom. A player wins if their card had a greater mana value.)

Heraldic Banner

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

Serpent of the Endless Sea

Serpent of the Endless Sea's power and toughness are each equal to the number of Islands you control.
This creature can't attack unless defending player controls an Island.

Cephalid Sage

Threshold — As long as seven or more cards are in your graveyard, this creature has "When this creature enters, draw three cards, then discard two cards."

Lingering Mirage

Enchant land
Enchanted land is an Island.
Cycling {2} ({2}, Discard this card: Draw a card.)

Sol Ring

Sky Diamond

This artifact enters tapped.
{T}: Add {U}.

Squid

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)

Sapphire Medallion

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

Segovian Leviathan

Walking Atlas

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

Swamp

Cephalid Pathmage

This creature can't be blocked.
{T}, Sacrifice this creature: Target creature can't be blocked this turn.

The Flood of Mars

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Water Always Wins — Whenever this creature attacks, put a flood counter on another target creature or land. If it's a creature, it becomes a copy of this creature. If it's a land, it becomes an Island in addition to its other types.

Nadir Kraken

Whenever you draw a card, you may pay {1}. If you do, put a +1/+1 counter on this creature and create a 1/1 blue Tentacle creature token.

Callous Oppressor

You may choose not to untap this creature during your untap step.
As this creature enters, an opponent chooses a creature type.
{T}: Gain control of target creature that isn't of the chosen type for as long as this creature remains tapped.

Island

Slinn Voda, the Rising Deep

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

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.

Spreading Seas

Enchant land
When this Aura enters, draw a card.
Enchanted land is an Island.

Giant Octopus

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.

Contaminated Aquifer

({T}: Add {U} or {B}.)
This land enters tapped.

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.

Tentacle

Tromokratis

Tromokratis has hexproof unless it's attacking or blocking.
Tromokratis can't be blocked unless all creatures defending player controls block it. (If any creature that player controls doesn't block this creature, it can't be blocked.)

Retraced Image

Reveal a card in your hand, then put that card onto the battlefield if it has the same name as a permanent.

Benthic Behemoth

Capsizing Wave

Return target creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

Sword Coast Serpent

This creature can't be blocked as long as you've cast a noncreature spell this turn.

Sword Coast Serpent // Capsizing Wave

Copy

(This token can be used to represent a token that's a copy of a permanent.)

Research the Deep

Draw a card. Clash with an opponent. If you win, return Research the Deep to its owner's hand. (Each clashing player reveals the top card of their library, then puts that card on their choice of the top or bottom. A player wins if their card had a greater mana value.)

Thought Vessel

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

Dimir Aqueduct

This land enters tapped.
When this land enters, return a land you control to its owner's hand.
{T}: Add {U}{B}.

Silver Raven

Flying
When this creature enters, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Aquitect's Will

Put a flood counter on target land. That land is an Island in addition to its other types for as long as it has a flood counter on it. If you control a Merfolk, draw a card.

Pearl Lake Ancient

Flash
This spell can't be countered.
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
Return three lands you control to their owner's hand: Return this creature to its owner's hand.

Star Compass

This artifact enters tapped.
{T}: Add one mana of any color that a basic land you control could produce.

Biolume Serpent

Sacrifice two Islands: This creature can't be blocked this turn.

Biolume Egg

Defender
When this creature enters, scry 2.
When you sacrifice this creature, return it to the battlefield transformed under its owner's control at the beginning of the next end step.

Biolume Egg // Biolume Serpent

Clue

Marvo, Deep Operative

Whenever Marvo attacks, clash with defending player. (Each clashing player reveals the top card of their library, then puts that card on their choice of the top or bottom. A player wins if their card had a greater mana value.)
Whenever you win a clash, draw a card. Then you may cast a spell from your hand with mana value 8 or less without paying its mana cost.

Shimmering Wings

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature has flying. (It can't be blocked except by creatures with flying or reach.)
{U}: Return this Aura to its owner's hand.

Stormsurge Kraken

Hexproof
Lieutenant — As long as you control your commander, this creature gets +2/+2 and has "Whenever this creature becomes blocked, you may draw two cards."

Kraken of the Straits

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

Wormhole Serpent

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

Flight

Enchant creature
Enchanted creature has flying.

Serpent of Yawning Depths

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

Sealock Monster

This creature can't attack unless defending player controls an Island.
{5}{U}{U}: Monstrosity 3. (If this creature isn't monstrous, put three +1/+1 counters on it and it becomes monstrous.)
When this creature becomes monstrous, target land becomes an Island in addition to its other types.

Revive the Fallen

Return target creature card from a graveyard to its owner's hand. Clash with an opponent. If you win, return Revive the Fallen to its owner's hand. (Each clashing player reveals the top card of their library, then puts that card on their choice of the top or bottom. A player wins if their card had a greater mana value.)

Chasm Skulker

Whenever you draw a card, put a +1/+1 counter on this creature.
When this creature dies, create X 1/1 blue Squid creature tokens with islandwalk, where X is the number of +1/+1 counters on this creature. (They can't be blocked as long as defending player controls an Island.)

Arcane Signet

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

Kraken

Dreamwinder

This creature can't attack unless defending player controls an Island.
{U}, Sacrifice an Island: Target land becomes an Island until end of turn.

Aboshan, Cephalid Emperor

Tap an untapped Octopus you control: Tap target permanent.
{U}{U}{U}: Tap all creatures without flying.

Bubble Smuggler

Disguise {5}{U} (You may cast this card face down for {3} as a 2/2 creature with ward {2}. Turn it face up any time for its disguise cost.)
As this creature is turned face up, put four +1/+1 counters on it.

Command Tower

Convincing Mirage

Enchant land
As this Aura enters, choose a basic land type.
Enchanted land is the chosen type.

Kiora's Dambreaker

When this creature enters, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)

Pulling Teeth

Clash with an opponent. If you win, target player discards two cards. Otherwise, that player discards a card. (Each clashing player reveals the top card of their library, then puts that card on their choice of the top or bottom. A player wins if their card had a greater mana value.)

Arcane Flight

Enchant creature
Enchanted creature gets +1/+1 and has flying.

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.

Frostwind Invoker

Flying
{8}: Creatures you control gain flying until end of turn.

Phantasmal Terrain

Terrain Generator

{T}: Add {C}.
{2}, {T}: You may put a basic land card from your hand onto the battlefield tapped.

Shield Broker

When this creature enters, put a shield counter on target noncommander creature you don't control. You gain control of that creature for as long as it has a shield counter on it. (If it would be dealt damage or destroyed, remove a shield counter from it instead.)

Grayscaled Gharial

Nemesis of Reason

Whenever this creature attacks, defending player mills ten cards.

Fishliver Oil

Enchant creature (Target a creature as you cast this. This card enters attached to that creature.)
Enchanted creature has islandwalk. (It can't be blocked as long as defending player controls an Island.)

Darkwater Catacombs

Psychic Pickpocket

When this creature enters, it connives. When it connives this way, return up to one target nonland permanent to its owner's hand. (To have a creature connive, draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on that creature.)

Dimir Guildgate

This land enters tapped.
{T}: Add {U} or {B}.

Godhunter Octopus

This creature can't attack unless defending player controls an enchantment or an enchanted permanent.

Augury Owl

Flying
When this creature enters, scry 3. (Look at the top three cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Coral Barrier

Defender (This creature can't attack.)
When this creature enters, create a 1/1 blue Squid creature token with islandwalk. (It can't be blocked as long as defending player controls an Island.)

Sea Monster

This creature can't attack unless defending player controls an Island.

Esior, Wardwing Familiar

Flying
Spells your opponents cast that target one or more commanders you control cost {3} more to cast.
Partner (You can have two commanders if both have partner.)

Jace's Phantasm

Flying
This creature gets +4/+4 as long as an opponent has ten or more cards in their graveyard.

Octoprophet

When this creature enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Part Water

X target creatures gain islandwalk until end of turn. (They can't be blocked as long as defending player controls an Island.)

Baleful Strix

Flying, deathtouch
When this creature enters, draw a card.

Charix, the Raging Isle

Spells your opponents cast that target Charix cost {2} more to cast.
{3}: Charix gets +X/-X until end of turn, where X is the number of Islands you control.

Cephalid Looter

{T}: Target player draws a card, then discards a card.

Sea's Claim

Enchant land (Target a land as you cast this. This card enters attached to that land.)
Enchanted land is an Island.

Merfolk Spy

Islandwalk (This creature can't be blocked as long as defending player controls an Island.)
Whenever this creature deals combat damage to a player, that player reveals a card at random from their hand.

Burnished Hart

{3}, Sacrifice this creature: Search your library for up to two basic land cards, put them onto the battlefield tapped, then shuffle.