Flooded Shoreline

{U}{U}, Return two Islands you control to their owner's hand: Return target creature to its owner's hand.

Island

Disrupt

Counter target instant or sorcery spell unless its controller pays {1}.
Draw a card.

Serrated Biskelion

{T}: Put a -1/-1 counter on Serrated Biskelion and a -1/-1 counter on target creature.

Boomerang

Return target permanent to its owner's hand.

Ray of Command

Untap target creature an opponent controls and gain control of it until end of turn. That creature gains haste until end of turn. When you lose control of the creature, tap it.

Power Sink

Counter target spell unless its controller pays {X}. If that player doesn't, they tap all lands with mana abilities they control and lose all unspent mana.

Knight of the Mists

Flanking (Whenever a creature without flanking blocks this creature, the blocking creature gets -1/-1 until end of turn.)
When Knight of the Mists enters, you may pay {U}. If you don't, destroy target Knight and it can't be regenerated.

Winding Canyons

{T}: Add {C}.
{2}, {T}: You may cast creature spells this turn as though they had flash.

Dream Tides

Creatures don't untap during their controllers' untap steps.
At the beginning of each player's upkeep, that player may choose any number of tapped nongreen creatures they control and pay {2} for each creature chosen this way. If the player does, untap those creatures.

Impulse

Look at the top four cards of your library. Put one of them into your hand and the rest on the bottom of your library in any order.

Abduction

Enchant creature
When Abduction enters, untap enchanted creature.
You control enchanted creature.
When enchanted creature dies, return that card to the battlefield under its owner's control.

Ophidian

Whenever Ophidian attacks and isn't blocked, you may draw a card. If you do, Ophidian assigns no combat damage this turn.

Quicksand

{T}: Add {C}.
{T}, Sacrifice Quicksand: Target attacking creature without flying gets -1/-2 until end of turn.

Dissipate

Counter target spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Vodalian Illusionist

{U}{U}, {T}: Target creature phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before its controller untaps during their next untap step.)

Man-o'-War

When Man-o'-War enters, return target creature to its owner's hand.

Waterspout Djinn

Flying
At the beginning of your upkeep, sacrifice Waterspout Djinn unless you return an untapped Island you control to its owner's hand.

Undo

Return two target creatures to their owners' hands.

Floodgate

Defender
When Floodgate has flying, sacrifice it.
When Floodgate leaves the battlefield, it deals damage to each nonblue creature without flying equal to half the number of Islands you control, rounded down.

Memory Lapse

Counter target spell. If that spell is countered this way, put it on top of its owner's library instead of into that player's graveyard.