Thassa's Rebuff

Counter target spell unless its controller pays {X}, where X is your devotion to blue. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Kasmina's Transmutation

Enchant creature
Enchanted creature loses all abilities and has base power and toughness 1/1.

Essence Scatter

Cryptic Serpent

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.

Thought Collapse

Counter target spell. Its controller mills three cards.

Counterspell

Tome Scour

Brainstorm

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

Didn't Say Please

Island

Dream Twist

Target player mills three cards.
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)