Ponder

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

Cowardice

Whenever a creature becomes the target of a spell or ability, return that creature to its owner's hand. (It won't be affected by the spell or ability.)

Harbinger of the Seas

Distorting Lens

{T}: Target permanent becomes the color of your choice until end of turn.

Wash Out

Return all permanents of the color of your choice to their owners' hands.

Heartstone

Activated abilities of creatures cost {1} less to activate. This effect can't reduce the mana in that cost to less than one mana.

Sway of Illusion

Any number of target creatures become the color of your choice until end of turn.
Draw a card.

Douse

Hydroblast

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

Eluge, the Shoreless Sea

Eluge's power and toughness are each equal to the number of Islands you control.
Whenever Eluge enters or attacks, put a flood counter on target land. It's an Island in addition to its other types for as long as it has a flood counter on it.
The first instant or sorcery spell you cast each turn costs {U} (or {1}) less to cast for each land you control with a flood counter on it.

Llawan, Cephalid Empress

When Llawan, Cephalid Empress enters, return all blue creatures your opponents control to their owners' hands.
Your opponents can't cast blue creature spells.

Flow of Knowledge

Draw a card for each Island you control, then discard two cards.

Brainstorm

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

Don't Make a Sound

Counter target spell unless its controller pays {2}. If they do, 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.)

King Crab

{1}{U}, {T}: Put target green creature on top of its owner's library.

Glimmerburst

Draw two cards. Create a 1/1 white Glimmer enchantment creature token.

Blind Seer

{1}{U}: Target spell or permanent becomes the color of your choice until end of turn.

Flash Flood

Choose one —
• Destroy target red permanent.
• Return target Mountain to its owner's hand.

Sapphire Medallion

Blue spells you cast cost {1} less to cast.

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Hibernation

Return all green permanents to their owners' hands.

Tidal Visionary

{T}: Target creature becomes the color of your choice until end of turn.

Willbreaker

Whenever a creature an opponent controls becomes the target of a spell or ability you control, gain control of that creature for as long as you control Willbreaker.

Blue Elemental Blast

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

Shifting Sky

As Shifting Sky enters, choose a color.
All nonland permanents are the chosen color.

Chill

Get Out

Choose one —
• Counter target creature or enchantment spell.
• Return one or two target creatures and/or enchantments you own to your hand.

Hullbreaker Horror

Flash
This spell can't be countered.
Whenever you cast a spell, choose up to one —
• Return target spell you don't control to its owner's hand.
• Return target nonland permanent to its owner's hand.

Jaded Response

Counter target spell if it shares a color with a creature you control.

Dismiss into Dream

Each creature your opponents control is an Illusion in addition to its other types and has "When this creature becomes the target of a spell or ability, sacrifice it."

Counterspell

Insight

Whenever an opponent casts a green spell, you draw a card.

Scuttlemutt

{T}: Add one mana of any color.
{T}: Target creature becomes the color or colors of your choice until end of turn.

High Tide

Until end of turn, whenever a player taps an Island for mana, that player adds an additional {U}.

Pongify

Destroy target creature. It can't be regenerated. Its controller creates a 3/3 green Ape creature token.