Snow-Covered Island

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.

Chorus of the Tides

Flying
Heroic — Whenever you cast a spell that targets Chorus of the Tides, scry 1. (To scry 1, look at the top card of your library, then you may put that card on the bottom.)

Winter's Chill

Cast this spell only during combat before blockers are declared.
X can't be greater than the number of snow lands you control.
Choose X target attacking creatures. For each of those creatures, its controller may pay {1} or {2}. If that player doesn't, destroy that creature at end of combat. If that player pays only {1}, prevent all combat damage that would be dealt to and dealt by that creature this combat.

Mistral Singer

Flying
Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)

Malcolm, Keen-Eyed Navigator

Flying
Whenever one or more Pirates you control deal damage to your opponents, you create a Treasure token for each opponent dealt damage. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")
Partner (You can have two commanders if both have partner.)

Sol Ring

Wall of Kelp

Defender (This creature can't attack.)
{U}{U}, {T}: Create a 0/1 blue Plant Wall creature token with defender named Kelp.

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.

Siren Song Lyre

Equipped creature has "{2}, {T}: Tap target creature."
Equip {2}

Siren Lookout

Flying
When Siren Lookout enters, it explores. (Reveal the top card of your library. Put that card into your hand if it's a land. Otherwise, put a +1/+1 counter on this creature, then put the card back or put it into your graveyard.)

Public Enemy

Enchant creature
All creatures attack enchanted creature's controller each combat if able.
When enchanted creature dies, draw a card.

Siren Reaver

Raid — This spell costs {1} less to cast if you attacked this turn.
Flying

Thought Vessel

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

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.

Crawlspace

No more than two creatures can attack you each combat.

Strixhaven Stadium

{T}: Add {C}. Put a point counter on Strixhaven Stadium.
Whenever a creature deals combat damage to you, remove a point counter from Strixhaven Stadium.
Whenever a creature you control deals combat damage to an opponent, put a point counter on Strixhaven Stadium. Then if it has ten or more point counters on it, remove them all and that player loses the game.

Fleet Swallower

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

Flow of Knowledge

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

Alluring Siren

{T}: Target creature an opponent controls attacks you this turn if able.

Scourge of Fleets

When Scourge of Fleets enters, 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.

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.

Tangle Kelp

Enchant creature
When Tangle Kelp enters, tap enchanted creature.
Enchanted creature doesn't untap during its controller's untap step if it attacked during its controller's last turn.

Distant Melody

Choose a creature type. Draw a card for each permanent you control of that type.

Maeve, Insidious Singer

{2}{U}: Goad target creature. Whenever that creature attacks one of your opponents this turn, you draw a card. (A goaded creature attacks each combat if able and attacks a player other than you if able, until your next turn.)

War-Wing Siren

Flying
Heroic — Whenever you cast a spell that targets War-Wing Siren, put a +1/+1 counter on War-Wing Siren.

Lookout's Dispersal

This spell costs {1} less to cast if you control a Pirate.
Counter target spell unless its controller pays {4}.

Deluge

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.

See Double

This spell can't be copied.
Choose one. If an opponent has eight or more cards in their graveyard, you may choose both instead.
• Copy target spell. You may choose new targets for the copy. (A copy of a permanent spell becomes a token.)
• Create a token that's a copy of target creature.

High Tide

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

Reins of Power

Untap all creatures you control and all creatures target opponent controls. You and that opponent each gain control of all creatures the other controls until end of turn. Those creatures gain haste until end of turn.

Whelming Wave

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

Aboshan, Cephalid Emperor

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

Zephyr Singer

Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.)
Flying, vigilance
When Zephyr Singer enters, put a flying counter on each creature that convoked it.

Hypnotic Siren

Bestow {5}{U}{U} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Flying
You control enchanted creature.
Enchanted creature gets +1/+1 and has flying.

Tidal Flats

{U}{U}: For each attacking creature without flying, its controller may pay {1}. If that player doesn't, creatures you control blocking that creature gain first strike until end of turn.

Ominous Seas

Whenever you draw a card, put a foreshadow counter on Ominous Seas.
Remove eight foreshadow counters from Ominous Seas: Create an 8/8 blue Kraken creature token.
Cycling {2} ({2}, Discard this card: Draw a card.)

Mocking Doppelganger

Flash
You may have Mocking Doppelganger enter as a copy of a creature an opponent controls, except it has "Other creatures with the same name as this creature are goaded." (They attack each combat if able and attack a player other than you if able.)

Dark Depths

Dark Depths enters with ten ice counters on it.
{3}: Remove an ice counter from Dark Depths.
When Dark Depths has no ice counters on it, sacrifice it. If you do, create Marit Lage, a legendary 20/20 black Avatar creature token with flying and indestructible.

Illusionist's Gambit

Cast this spell only during the declare blockers step on an opponent's turn.
Remove all attacking creatures from combat and untap them. After this phase, there is an additional combat phase. Each of those creatures attacks that combat if able. They can't attack you or planeswalkers you control that combat.

Training Grounds

Activated abilities of creatures you control cost {2} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Portal Mage

Flash
When Portal Mage enters during the declare attackers step, you may reselect which player or permanent target attacking creature is attacking. (It can't attack its controller or their permanents.)

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.

Siren Stormtamer

Flying
{U}, Sacrifice Siren Stormtamer: Counter target spell or ability that targets you or a creature you control.

Propaganda

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

Dulcet Sirens

{U}, {T}: Target creature attacks target opponent this turn if able.
Morph {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.)

Arcane Signet

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

Cloaked Siren

Flash (You may cast this spell any time you could cast an instant.)
Flying

Whispers of the Muse

Buyback {5} (You may pay an additional {5} as you cast this spell. If you do, put this card into your hand as it resolves.)
Draw a card.

Pursued Whale

When Pursued Whale enters, each opponent creates a 1/1 red Pirate creature token with "This creature can't block" and "Creatures you control attack each combat if able."
Spells your opponents cast that target Pursued Whale cost {3} more to cast.

Aetherspouts

For each attacking creature, its owner puts it on their choice of the top or bottom of their library.

Disdainful Stroke

Counter target spell with mana value 4 or greater.

Threnody Singer

Flash
Flying
When Threnody Singer enters, target creature an opponent controls gets -X/-0 until end of turn, where X is your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Vedalken Shackles

You may choose not to untap Vedalken Shackles during your untap step.
{2}, {T}: Gain control of target creature with power less than or equal to the number of Islands you control for as long as Vedalken Shackles remains tapped.

Piracy

Until end of turn, you may tap lands you don't control for mana. Spend this mana only to cast spells.

Dreamcaller Siren

Flash
Flying
Dreamcaller Siren can block only creatures with flying.
When Dreamcaller Siren enters, if you control another Pirate, tap up to two target nonland permanents.

Entrancing Melody

Gain control of target creature with mana value X.

Siren of the Fanged Coast

Flying
Tribute 3 (As this creature enters, an opponent of your choice may put three +1/+1 counters on it.)
When Siren of the Fanged Coast enters, if tribute wasn't paid, gain control of target creature.