Consider

Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
Draw a card.

Annul

Counter target artifact or enchantment spell.

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.)

Murmuring Mystic

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

Steel Sabotage

Choose one —
• Counter target artifact spell.
• Return target artifact to its owner's hand.

Fate Transfer

Move all counters from target creature onto another target creature.

Mental Note

Nullify

Island

Artful Dodge

Target creature can't be blocked this turn.
Flashback {U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Brainstorm

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

Dragon Wings

Enchant creature
Enchanted creature has flying.
Cycling {1}{U} ({1}{U}, Discard this card: Draw a card.)
When a creature with mana value 6 or greater enters, you may return Dragon Wings from your graveyard to the battlefield attached to that creature.

Spell Pierce

Counter target noncreature spell unless its controller pays {2}.

Hydroblast

Choose one —
• Counter target spell if it's red.
• Destroy target permanent if it's red.

Insectile Aberration

Delver of Secrets

At the beginning of your upkeep, look at the top card of your library. You may reveal that card. If an instant or sorcery card is revealed this way, transform Delver of Secrets.

Delver of Secrets // Insectile Aberration

Echoing Truth

Return target nonland permanent and all other permanents with the same name as that permanent to their owners' hands.

Dispel

Otherworldly Gaze

Surveil 3. (Look at the top three cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)
Flashback {1}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Thought Scour

Target player mills two cards.
Draw a card.

Blue Elemental Blast

Choose one —
• Counter target red spell.
• Destroy target red permanent.

Snap

Return target creature to its owner's hand. Untap up to two lands.

Sleep of the Dead

Tap target creature. It doesn't untap during its controller's next untap step.
Escape—{2}{U}, Exile three other cards from your graveyard. (You may cast this card from your graveyard for its escape cost.)

Counterspell

Cryptic Serpent

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

Tolarian Terror

This spell costs {1} less to cast for each instant and sorcery card in your graveyard.
Ward {2} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {2}.)

Deem Inferior

This spell costs {1} less to cast for each card you've drawn this turn.
The owner of target nonland permanent puts it into their library second from the top or on the bottom.

Boomerang

Return target permanent to its owner's hand.

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.)