Island

Unsummon

Return target creature to its owner's hand.

Tidal Warrior

{T}: Target land becomes an Island until end of turn.

Annul

Counter target artifact or enchantment spell.

Lord of Atlantis

Other Merfolk get +1/+1 and have islandwalk. (They can't be blocked as long as defending player controls an Island.)

Counterspell

Accumulated Knowledge

Draw a card, then draw cards equal to the number of cards named Accumulated Knowledge in all graveyards.

Hibernation

Return all green permanents to their owners' hands.

Misdirection

You may exile a blue card from your hand rather than pay this spell's mana cost.
Change the target of target spell with a single target.

Lonely Sandbar

Lonely Sandbar enters tapped.
{T}: Add {U}.
Cycling {U} ({U}, Discard this card: Draw a card.)

Merfolk Traders

When Merfolk Traders enters, draw a card, then discard a card.

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Gush

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

Manta Riders

{U}: Manta Riders gains flying until end of turn.

Tormod's Crypt

{T}, Sacrifice Tormod's Crypt: Exile target player's graveyard.

Rootwater Hunter

{T}: Rootwater Hunter deals 1 damage to any target.

Merfolk Looter

Wasteland

{T}: Add {C}.
{T}, Sacrifice Wasteland: Destroy target nonbasic land.

Vodalian Merchant

When Vodalian Merchant enters, draw a card, then discard a card.

Waterfront Bouncer

{U}, {T}, Discard a card: Return target creature to its owner's hand.

Force of Will

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.
Counter target spell.

Submerge

If an opponent controls a Forest and you control an Island, you may cast this spell without paying its mana cost.
Put target creature on top of its owner's library.