Consider

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

Force Away

Return target creature to its owner's hand.
Ferocious — If you control a creature with power 4 or greater, you may draw a card. If you do, discard a card.

Serpentine Curve

Create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it, where X is one plus the total number of instant and sorcery cards you own in exile and in your graveyard.

Spell Pierce

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

Careful Study

Haunted Cloak

Equipped creature has vigilance, trample, and haste.
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)

Spectral Flight

Enchant creature
Enchanted creature gets +2/+2 and has flying.

Lonely Sandbar

Lonely Sandbar enters tapped.
{T}: Add {U}.
Cycling {U} ({U}, Discard this card: Draw a card.)

Disrupt

Counter target instant or sorcery spell unless its controller pays {1}.
Draw a card.

Compelling Argument

Target player mills five cards.
Cycling {U} ({U}, Discard this card: Draw a card.)

Think Twice

Draw a card.
Flashback {2}{U} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Mana Leak

Counter target spell unless its controller pays {3}.

Memory Lapse

Counter target spell. If that spell is countered this way, put it on top of its owner's library instead of into that player's graveyard.

Flash Counter

Merchant Scroll

Search your library for a blue instant card, reveal that card, put it into your hand, then shuffle.

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.)

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.)

Opal Palace

{T}: Add {C}.
{1}, {T}: Add one mana of any color in your commander's color identity. If you spend this mana to cast your commander, it enters with a number of additional +1/+1 counters on it equal to the number of times it's been cast from the command zone this game.

Thought Scour

Target player mills two cards.
Draw a card.

Miscalculation

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

Hard Evidence

Create a 0/3 blue Crab creature token.
Investigate. (Create a Clue token. It's an artifact with "{2}, Sacrifice this artifact: Draw a card.")

You Come to a River

Choose one —
• Fight the Current — Return target nonland permanent to its owner's hand.
• Find a Crossing — Target creature gets +1/+0 until end of turn and can't be blocked this turn.

Muddle the Mixture

Counter target instant or sorcery spell.
Transmute {1}{U}{U} ({1}{U}{U}, Discard this card: Search your library for a card with the same mana value as this card, reveal it, put it into your hand, then shuffle. Transmute only as a sorcery.)

Intervene

Counter target spell that targets a creature.

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.

Treasure Cruise

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Draw three cards.

Echoing Truth

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

Gush

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

Slip Through Space

Devoid (This card has no color.)
Target creature can't be blocked this turn.
Draw a card.

Scry 1. (Look at the top card of your library. You may put that card on the bottom.)
Draw a card.

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.

Cartouche of Knowledge

Enchant creature you control
When Cartouche of Knowledge enters, draw a card.
Enchanted creature gets +1/+1 and has flying.

One With the Wind

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.

Deprive

As an additional cost to cast this spell, return a land you control to its owner's hand.
Counter target spell.

Sailors' Bane

This spell costs {1} less to cast for each card you own in exile and in your graveyard that's an instant card, a sorcery card, or a card that has an Adventure.
Ward {4} (Whenever this creature becomes the target of a spell or ability an opponent controls, counter it unless that player pays {4}.)

Frantic Search

Draw two cards, then discard two cards. Untap up to three lands.

Maximize Altitude

Target creature gets +1/+1 and gains flying until end of turn.
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.)

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}.)

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

Strategic Planning

Look at the top three cards of your library. Put one of them into your hand and the rest into your graveyard.

Ponder

Look at the top three cards of your library, then put them back in any order. You may shuffle.
Draw a card.

Mental Note

Hieroglyphic Illumination

Draw two cards.
Cycling {U} ({U}, Discard this card: Draw a card.)

Tolarian Winds

Discard all the cards in your hand, then draw that many cards.

Spell Rupture

Counter target spell unless its controller pays {X}, where X is the greatest power among creatures you control.

Prohibit

Kicker {2} (You may pay an additional {2} as you cast this spell.)
Counter target spell if its mana value is 2 or less. If this spell was kicked, counter that spell if its mana value is 4 or less instead.

Serum Visions

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}.

Dispersal Shield

Counter target spell if its mana value is less than or equal to the highest mana value among permanents you control.

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}.

Dispel

Shadow Rift

Target creature gains shadow until end of turn. (It can block or be blocked by only creatures with shadow.)
Draw a card.

Into the Roil

Boomerang

Return target permanent to its owner's hand.

Portent

Look at the top three cards of target player's library, then put them back in any order. You may have that player shuffle.
Draw a card at the beginning of the next turn's upkeep.

Command Performance

Choose two —
• Open an Attraction. (Put the top card of your Attraction deck onto the battlefield.)
• Roll to visit your Attractions.
• You get {TK}{TK}.
• You may put a sticker on a nonland permanent you own.

Negate

Veil of Secrecy

Target creature gains shroud until end of turn and can't be blocked this turn. (A creature with shroud can't be the target of spells or abilities.)
Splice onto Arcane—Return a blue creature you control to its owner's hand. (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Arcane Denial

Counter target spell. Its controller may draw up to two cards at the beginning of the next turn's upkeep.
You draw a card at the beginning of the next turn's upkeep.

Sapphire Charm

Choose one —
• Target player draws a card at the beginning of the next turn's upkeep.
• Target creature gains flying until end of turn.
• Target creature an opponent controls phases out. (While it's phased out, it's treated as though it doesn't exist. It phases in before its controller untaps during their next untap step.)

Brainstorm

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

You See a Guard Approach

Choose one —
• Distract the Guard — Tap target creature.
• Hide — Target creature you control gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Distortion Strike

Target creature gets +1/+0 until end of turn and can't be blocked this turn.
Rebound (If you cast this spell from your hand, exile it as it resolves. At the beginning of your next upkeep, you may cast this card from exile without paying its mana cost.)

Arcane Flight

Enchant creature
Enchanted creature gets +1/+1 and has flying.

Foresight

Search your library for three cards, exile them, then shuffle.
Draw a card at the beginning of the next turn's upkeep.

Dive Down

Target creature you control gets +0/+3 and gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)

Sleight of Hand

Look at the top two cards of your library. Put one of them into your hand and the other on the bottom of your library.

Preordain

Scry 2, then draw a card. (To 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.)

Island

Gitaxian Probe

({U/P} can be paid with either {U} or 2 life.)
Look at target player's hand.
Draw a card.

Logic Knot

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Counter target spell unless its controller pays {X}.

Mizzium Skin

Target creature you control gets +0/+1 and gains hexproof until end of turn.
Overload {1}{U} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Curate

Surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)
Draw a card.

Winds of Rebuke

Return target nonland permanent to its owner's hand. Each player mills two cards.