Morphling

{U}: Untap this creature.
{U}: This creature gains flying until end of turn.
{U}: This creature gains shroud until end of turn. (It can't be the target of spells or abilities.)
{1}: This creature gets +1/-1 until end of turn.
{1}: This creature gets -1/+1 until end of turn.

Temporal Adept

{U}{U}{U}, {T}: Return target permanent to its owner's hand.

Brilliant Plan

Opportunity

Stronghold Biologist

{U}{U}, {T}, Discard a card: Counter target creature spell.

Gush

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

Quash

Counter target instant or sorcery spell. Search its controller's graveyard, hand, and library for all cards with the same name as that spell and exile them. Then that player shuffles.

Rethink

Counter target spell unless its controller pays {X}, where X is its mana value.

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.

Preemptive Strike

Miscalculation

Counter target spell unless its controller pays {2}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Spiketail Drake

Flying
Sacrifice this creature: Counter target spell unless its controller pays {3}.

Foil

You may discard an Island card and another card rather than pay this spell's mana cost.
Counter target spell.

Faerie Conclave

This land enters tapped.
{T}: Add {U}.
{1}{U}: This land becomes a 2/1 blue Faerie creature with flying until end of turn. It's still a land.

Rhystic Study

Whenever an opponent casts a spell, you may draw a card unless that player pays {1}.

Accumulated Knowledge

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

Rewind

Counter target spell. Untap up to four lands.

Brainstorm

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

Island

Spell Blast

Counter target spell with mana value X. (For example, if that spell's mana cost is {3}{U}{U}, X is 5.)

Remove Soul

Stroke of Genius

Counterspell

Stronghold Machinist

{U}{U}, {T}, Discard a card: Counter target noncreature spell.

Inspiration

Avatar of Will

If an opponent has no cards in hand, this spell costs {6} less to cast.
Flying

Disruptive Student

{T}: Counter target spell unless its controller pays {1}.

Seal of Removal

Sacrifice this enchantment: Return target creature to its owner's hand.

Daze

You may return an Island you control to its owner's hand rather than pay this spell's mana cost.
Counter target spell unless its controller pays {1}.

Boomerang

Return target permanent to its owner's hand.

Desertion

Counter target spell. If an artifact or creature spell is countered this way, put that card onto the battlefield under your control instead of into its owner's graveyard.

Archivist

Spiketail Hatchling

Flying (This creature can't be blocked except by creatures with flying or reach.)
Sacrifice this creature: Counter target spell unless its controller pays {1}.

Scent of Brine

Reveal any number of blue cards in your hand. Counter target spell unless its controller pays {1} for each card revealed this way.

Psychic Theft

Target player reveals their hand. You choose an instant or sorcery card from it and exile that card. You may cast that card for as long as it remains exiled. At the beginning of the next end step, if you haven't cast the card, return it to its owner's hand.