Force of Will

You may pay 1 life and exile a blue card from your hand rather than pay this spell's mana cost.
Counter target spell.

Dauthi Voidwalker

Shadow (This creature can block or be blocked by only creatures with shadow.)
If a card would be put into an opponent's graveyard from anywhere, instead exile it with a void counter on it.
{T}, Sacrifice Dauthi Voidwalker: Choose an exiled card an opponent owns with a void counter on it. You may play it this turn without paying its mana cost.

Lotus Petal

{T}, Sacrifice Lotus Petal: Add one mana of any color.

Hurkyl's Recall

Return all artifacts target player owns to their hand.

Polluted Delta

{T}, Pay 1 life, Sacrifice Polluted Delta: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

Pest Control

Destroy all nonland permanents with mana value 1 or less.
Cycling {2} ({2}, Discard this card: Draw a card.)

Massacre

If an opponent controls a Plains and you control a Swamp, you may cast this spell without paying its mana cost.
All creatures get -2/-2 until end of turn.

Petty Theft

Return target nonland permanent an opponent controls to its owner's hand.

Brazen Borrower

Flash
Flying
Brazen Borrower can block only creatures with flying.

Brazen Borrower // Petty Theft

Flusterstorm

Counter target instant or sorcery spell unless its controller pays {1}.
Storm (When you cast this spell, copy it for each spell cast before it this turn. You may choose new targets for the copies.)

Vexing Bauble

Whenever a player casts a spell, if no mana was spent to cast it, counter that spell.
{1}, {T}, Sacrifice Vexing Bauble: Draw a card.

Island

Scrubland

Unearth

Return target creature card with mana value 3 or less from your graveyard to the battlefield.
Cycling {2} ({2}, Discard this card: Draw a card.)

Thassa's Oracle

When Thassa's Oracle enters, look at the top X cards of your library, where X is your devotion to blue. Put up to one of them on top of your library and the rest on the bottom of your library in a random order. If X is greater than or equal to the number of cards in your library, you win the game. (Each {U} in the mana costs of permanents you control counts toward your devotion to blue.)

Consider

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

Thoughtseize

Target player reveals their hand. You choose a nonland card from it. That player discards that card. You lose 2 life.

Swamp

Nihil Spellbomb

{T}, Sacrifice Nihil Spellbomb: Exile target player's graveyard.
When Nihil Spellbomb is put into a graveyard from the battlefield, you may pay {B}. If you do, draw a card.

Brainstorm

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

Tundra

Ponder

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

Doomsday

Search your library and graveyard for five cards and exile the rest. Put the chosen cards on top of your library in any order. You lose half your life, rounded up.

Marsh Flats

{T}, Pay 1 life, Sacrifice Marsh Flats: Search your library for a Plains or Swamp card, put it onto the battlefield, then shuffle.

Swords to Plowshares

Exile target creature. Its controller gains life equal to its power.

Psychic Frog

Whenever Psychic Frog deals combat damage to a player or planeswalker, draw a card.
Discard a card: Put a +1/+1 counter on Psychic Frog.
Exile three cards from your graveyard: Psychic Frog gains flying until end of turn.

Force of Negation

If it's not your turn, you may exile a blue card from your hand rather than pay this spell's mana cost.
Counter target noncreature spell. If that spell is countered this way, exile it instead of putting it into its owner's graveyard.

Murktide Regent

Delve (Each card you exile from your graveyard while casting this spell pays for {1}.)
Flying
Murktide Regent enters with a +1/+1 counter on it for each instant and sorcery card exiled with it.
Whenever an instant or sorcery card leaves your graveyard, put a +1/+1 counter on Murktide Regent.

Barrowgoyf

Deathtouch, lifelink
Barrowgoyf's power is equal to the number of card types among cards in all graveyards and its toughness is equal to that number plus 1.
Whenever Barrowgoyf deals combat damage to a player, you may mill that many cards. If you do, you may put a creature card from among them into your hand.

Underground Sea

Orcish Bowmasters

Flash
When Orcish Bowmasters enters and whenever an opponent draws a card except the first one they draw in each of their draw steps, Orcish Bowmasters deals 1 damage to any target. Then amass Orcs 1.

Dark Ritual

Hydroblast

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

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}.

Undercity Sewers

({T}: Add {U} or {B}.)
Undercity Sewers enters tapped.
When Undercity Sewers enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Flooded Strand

{T}, Pay 1 life, Sacrifice Flooded Strand: Search your library for a Plains or Island card, put it onto the battlefield, then shuffle.