Unsummon

Return target creature to its owner's hand.

Sweet Oblivion

Target player mills four cards.
Escape—{3}{U}, Exile four other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)

Drowned Secrets

Whenever you cast a blue spell, target player mills two cards.

Murmuring Mystic

Whenever you cast an instant or sorcery spell, create a 1/1 blue Bird Illusion creature token with flying.

Mystic Sanctuary

({T}: Add {U}.)
Mystic Sanctuary enters tapped unless you control three or more other Islands.
When Mystic Sanctuary enters untapped, you may put target instant or sorcery card from your graveyard on top of your library.

Chemister's Insight

Draw two cards.
Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)

Windstorm Drake

Flying
Other creatures you control with flying get +1/+0.

Stern Dismissal

Return target creature or enchantment an opponent controls to its owner's hand.

Negate

Ashiok, Dream Render

Spells and abilities your opponents control can't cause their controller to search their library.
−1: Target player mills four cards. Then exile each opponent's graveyard.

Overwhelmed Apprentice

When Overwhelmed Apprentice enters, each opponent mills two cards. Then you scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)

Witching Well

When Witching Well enters, scry 2. (Look at the top two cards of your library, then put any number of them on the bottom and the rest on top in any order.)
{3}{U}, Sacrifice Witching Well: Draw two cards.

Venture Deeper

Target player mills four cards. (Then exile this card. You may cast the creature later from exile.)

Merfolk Secretkeeper

Merfolk Secretkeeper // Venture Deeper

Jace, Wielder of Mysteries

If you would draw a card while your library has no cards in it, you win the game instead.
+1: Target player mills two cards. Draw a card.
−8: Draw seven cards. Then if your library has no cards in it, you win the game.

Didn't Say Please

Counter target spell. Its controller mills three cards.

Thought Collapse

Augur of Bolas

When Augur of Bolas enters, look at the top three cards of your library. You may reveal an instant or sorcery card from among them and put it into your hand. Put the rest on the bottom of your library in any order.

Into the Story

This spell costs {3} less to cast if an opponent has seven or more cards in their graveyard.
Draw four cards.

Sage's Row Denizen

Whenever another blue creature you control enters, target player mills two cards.