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.)

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 this card: Counter target spell or ability unless its controller pays {3}.

Wash Out

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

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}: This creature can't be blocked this turn. Activate only if you own a card in exile.

Fortress Crab

Uchuulon

Uchuulon's power is equal to the number of Crabs, Oozes, and/or Horrors you control.
Horrific Symbiosis — At the beginning of your end step, exile up to one target creature card from an opponent's graveyard. If you do, create a token that's a copy of this creature.

High Tide

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

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.)
Whenever this creature or enchanted creature deals combat damage to a player, draw a card.
Enchanted creature gets +3/+3.

Deepmuck Desperado

Whenever you commit a crime, each opponent mills three cards. This ability triggers only once each turn. (Targeting opponents, anything they control, and/or cards in their graveyards is a crime.)

Griptide

Put target creature on top of its owner's library.

Hedron Crab

Landfall — Whenever a land you control enters, target player mills three cards. (They put the top three cards of their library into their graveyard.)

Ancient Crab

Crabomination

Emerge from artifact {5}{B}{B} (You may cast this spell by sacrificing an artifact and paying the emerge cost reduced by that artifact's mana value.)
When this creature enters, target opponent exiles the top card of their library, a card at random from their graveyard, and a card at random from their hand. You may cast a spell from among cards exiled this way without paying its mana cost.

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.

Iceberg Cancrix

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

Wishcoin Crab

Crystacean

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

Snow-Covered Island

Submerged Boneyard

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

Shorecomber Crab

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.