Retreat to Coralhelm

Landfall — Whenever a land you control enters, choose one —
• You may tap or untap target creature.
• Scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Reverse the Polarity

Choose one —
• Counter all other spells.
• Switch each creature's power and toughness until end of turn.
• Creatures can't be blocked this turn.

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.

Into the Roil

Kicker {1}{U} (You may pay an additional {1}{U} as you cast this spell.)
Return target nonland permanent to its owner's hand. If this spell was kicked, draw a card.

Dive Down

Target creature you control gets +0/+3 and gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Wishcoin Crab

Filter Out

Return all noncreature, nonland permanents to their owners' hands.

Giant Crab

{U}: Giant Crab gains shroud until end of turn. (It can't be the target of spells or abilities.)

Wash Away

Cleave {1}{U}{U} (You may cast this spell for its cleave cost. If you do, remove the words in square brackets.)
Counter target spell [that wasn't cast from its owner's hand].

Fierce Guardianship

If you control a commander, you may cast this spell without paying its mana cost.
Counter target noncreature spell.

Fabricate

Search your library for an artifact card, reveal it, put it into your hand, then shuffle.

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Flow of Ideas

Roaming Throne

Ward {2}
As Roaming Throne enters, choose a creature type.
Roaming Throne is the chosen type in addition to its other types.
If a triggered ability of another creature you control of the chosen type triggers, it triggers an additional time.

Keep Safe

Counter target spell that targets a permanent you control.
Draw a card.

Coat of Arms

Each creature gets +1/+1 for each other creature on the battlefield that shares at least one creature type with it. (For example, if two Goblin Warriors and a Goblin Shaman are on the battlefield, each gets +2/+2.)

Wormfang Crab

Wormfang Crab can't be blocked.
When Wormfang Crab enters, an opponent chooses a permanent you control other than Wormfang Crab and exiles it.
When Wormfang Crab leaves the battlefield, return the exiled card to the battlefield under its owner's control.

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.

Charix, the Raging Isle

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

Mirelurk Queen

Vigilance
When Mirelurk Queen enters, target player gets two rad counters.
Whenever one or more nonland cards are milled, draw a card, then put a +1/+1 counter on Mirelurk Queen. This ability triggers only once each turn.

Crystacean

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

Chromeshell Crab

Morph {4}{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.)
When Chromeshell Crab is turned face up, you may exchange control of target creature you control and target creature an opponent controls.

Hedron Crab

Landfall — Whenever a land you control enters, target player mills three cards.

Fortress Crab

Propaganda

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

Brainstorm

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

Twisted Image

Switch target creature's power and toughness until end of turn.
Draw a card.

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.

Dreadlight Monstrosity

Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)
{3}{U}{U}: Dreadlight Monstrosity can't be blocked this turn. Activate only if you own a card in exile.

Sapphire Medallion

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

Instruments of War

Flash
As Instruments of War enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.

Skitter Eel

{2}{U}: Adapt 2. (If this creature has no +1/+1 counters on it, put two +1/+1 counters on it.)

Vanquisher's Banner

As Vanquisher's Banner enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
Whenever you cast a creature spell of the chosen type, draw a card.

Thassa's Emissary

Bestow {5}{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.)
Whenever Thassa's Emissary or enchanted creature deals combat damage to a player, draw a card.
Enchanted creature gets +3/+3.

Flow of Knowledge

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

Kindred Discovery

As Kindred Discovery enters, choose a creature type.
Whenever a creature you control of the chosen type enters or attacks, draw a card.

Mirrorshell Crab

Ward {3} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {3}.)
Channel — {2}{U}, Discard Mirrorshell Crab: Counter target spell or ability unless its controller pays {3}.

Aether Tunnel

Enchant creature
Enchanted creature gets +1/+0 and can't be blocked.

Vexing Scuttler

Emerge {6}{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, you may return target instant or sorcery card from your graveyard to your hand.

Ruin Crab

Landfall — Whenever a land you control enters, each opponent mills three cards. (To mill a card, a player puts the top card of their library into their graveyard.)

Hightide Hermit

Defender
When Hightide Hermit enters, you get {E}{E}{E}{E} (four energy counters).
Pay {E}{E}: Hightide Hermit can attack this turn as though it didn't have defender.

Loxodon Warhammer

Equipped creature gets +3/+0 and has trample and lifelink.
Equip {3}

Door of Destinies

As Door of Destinies enters, choose a creature type.
Whenever you cast a spell of the chosen type, put a charge counter on Door of Destinies.
Creatures you control of the chosen type get +1/+1 for each charge counter on Door of Destinies.

Fumble

Return target creature to its owner's hand. Gain control of all Auras and Equipment that were attached to it, then attach them to another creature.

Imprisoned in the Moon

Enchant creature, land, or planeswalker
Enchanted permanent is a colorless land with "{T}: Add {C}" and loses all other card types and abilities.

Engulf the Shore

Return to their owners' hands all creatures with toughness less than or equal to the number of Islands you control.

Shore Up

Target creature you control gets +1/+1 and gains hexproof until end of turn. Untap it. (It can't be the target of spells or abilities your opponents control.)

High Tide

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

Iceberg Cancrix

Whenever another snow permanent you control enters, you may have target player mill two cards.

Skittering Crustacean

{6}{U}: Monstrosity 4. (If this creature isn't monstrous, put four +1/+1 counters on it and it becomes monstrous.)
As long as Skittering Crustacean is monstrous, it has hexproof. (It can't be the target of spells or abilities your opponents control.)

Crab Umbra

Enchant creature
{2}{U}: Untap enchanted creature.
Umbra armor (If enchanted creature would be destroyed, instead remove all damage from it and destroy this Aura.)

Slip Through Space

Devoid (This card has no color.)
Target creature can't be blocked this turn.
Draw a card.

Call to the Kindred

Enchant creature
At the beginning of your upkeep, you may look at the top five cards of your library. If you do, you may put a creature card that shares a creature type with enchanted creature from among them onto the battlefield, then you put the rest of those cards on the bottom of your library in any order.

Explorer's Scope

Whenever equipped creature attacks, look at the top card of your library. If it's a land card, you may put it onto the battlefield tapped.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Wonder

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

Winged Boots

Equipped creature has flying and ward {4}. (Whenever equipped creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {4}.)
Equip {1}

King Crab

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

Canyon Crab

{1}{U}: Canyon Crab gets +2/-2 until end of turn.
At the beginning of your end step, if you haven't cast a spell from your hand this turn, draw a card, then discard a card.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Ichthyomorphosis

Enchant creature
Enchanted creature loses all abilities and is a blue Fish with base power and toughness 0/1.

Ancient Crab

Icon of Ancestry

As Icon of Ancestry enters, choose a creature type.
Creatures you control of the chosen type get +1/+1.
{3}, {T}: Look at the top three cards of your library. You may reveal a creature card of the chosen type from among them and put it into your hand. Put the rest on the bottom of your library in a random order.

Jwari Scuttler

Out of Air

This spell costs {2} less to cast if it targets a creature spell.
Counter target spell.

Horseshoe Crab

Herald's Horn

As Herald's Horn enters, choose a creature type.
Creature spells you cast of the chosen type cost {1} less to cast.
At the beginning of your upkeep, look at the top card of your library. If it's a creature card of the chosen type, you may reveal it and put it into your hand.

Aetherspouts

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

Fae Flight

Flash
Enchant creature
When Fae Flight enters, enchanted creature gains hexproof until end of turn.
Enchanted creature gets +1/+0 and has flying.

Treasure Cruise

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Draw three cards.

Sword Coast Sailor

Commander creatures you own have "Whenever this creature attacks a player, if no opponent has more life than that player, this creature can't be blocked this turn."

Oraxid

Shell Shield

Kicker {1} (You may pay an additional {1} as you cast this spell.)
Target creature you control gets +0/+3 until end of turn. If this spell was kicked, that creature also gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Scuttletide

{1}, Discard a card: Create a 0/3 blue Crab creature token.
Delirium — Crabs you control get +1/+1 as long as there are four or more card types among cards in your graveyard.

Reflections of Littjara

As Reflections of Littjara enters, choose a creature type.
Whenever you cast a spell of the chosen type, copy that spell. (A copy of a permanent spell becomes a token.)

Fireshrieker

Equipped creature has double strike. (It deals both first-strike and regular combat damage.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Aqueous Form

Enchant creature
Enchanted creature can't be blocked.
Whenever enchanted creature attacks, scry 1. (Look at the top card of your library. You may put that card on the bottom.)

Distant Melody

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

Frogify

Enchant creature
Enchanted creature loses all abilities and is a blue Frog creature with base power and toughness 1/1. (It loses all other card types and creature types.)

Eaten by Piranhas

Flash
Enchant creature
Enchanted creature loses all abilities and is a black Skeleton creature with base power and toughness 1/1. (It loses all other card types and creature types.)

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.

Hard Evidence

Create a 0/3 blue Crab creature token.
Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

Bloodline Pretender

Changeling (This card is every creature type.)
As Bloodline Pretender enters, choose a creature type.
Whenever another creature you control of the chosen type enters, put a +1/+1 counter on Bloodline Pretender.

Armored Cancrix

Bitterthorn, Nissa's Animus

Living weapon (When this Equipment enters, create a 0/0 black Phyrexian Germ creature token, then attach this to it.)
Equipped creature gets +1/+1.
Whenever equipped creature attacks, you may search your library for a basic land card, put it onto the battlefield tapped, then shuffle.
Equip {3}

Obelisk of Urd

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.)
As Obelisk of Urd enters, choose a creature type.
Creatures you control of the chosen type get +2/+2.

Wash Out

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

Ponder

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

Gush

You may return two Islands you control to their owner's hand rather than pay this spell's mana cost.
Draw two cards.

Levitation

Commander's Plate

Equipped creature gets +3/+3 and has protection from each color that's not in your commander's color identity.
Equip commander {3}
Equip {5}

Purple-Crystal Crab

When Purple-Crystal Crab dies, draw a card.

Drownyard Behemoth

Flash (You may cast this spell any time you could cast an instant.)
Emerge {7}{U} (You may cast this spell by sacrificing a creature and paying the emerge cost reduced by that creature's mana value.)
Drownyard Behemoth has hexproof as long as it entered this turn.

Preordain

Scry 2, then draw a card. (To 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.)

Salvage Scuttler

Whenever Salvage Scuttler attacks, return an artifact you control to its owner's hand.