Counterspell

Quick Study

Island

Mana Leak

Counter target spell unless its controller pays {3}.

Blink of an Eye

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.

Brainstorm

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

Sand Augury

Scry 1, then draw a card. (Then exile this card. You may cast the creature later from exile.)

Young Blue Dragon

Young Blue Dragon // Sand Augury

Read the Tides

Choose one —
• Draw three cards.
• Return up to two target creatures to their owners' hands.

Lose Focus

Replicate {U} (When you cast this spell, copy it for each time you paid its replicate cost. You may choose new targets for the copies.)
Counter target spell unless its controller pays {2}.

Capsizing Wave

Return target creature to its owner's hand. (Then exile this card. You may cast the creature later from exile.)

Sword Coast Serpent

This creature can't be blocked as long as you've cast a noncreature spell this turn.

Sword Coast Serpent // Capsizing Wave

Deep Analysis

Target player draws two cards.
Flashback—{1}{U}, Pay 3 life. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Into the Roil

Giant Koi

Waterbend {3}: This creature can't be blocked this turn. (While paying a waterbend cost, you can tap your artifacts and creatures to help. Each one pays for {1}.)
Islandcycling {2} ({2}, Discard this card: Search your library for an Island card, reveal it, put it into your hand, then shuffle.)

Force Spike

Counter target spell unless its controller pays {1}.

Gone Missing

Put target permanent on top of its owner's library.
Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this token: Draw a card.")

Lórien Revealed

Draw three cards.
Islandcycling {1} ({1}, Discard this card: Search your library for an Island card, reveal it, put it into your hand, then shuffle.)

Lost Days

The owner of target creature or enchantment puts it into their library second from the top or on the bottom. You create a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")