Restless Reef

This land enters tapped.
{T}: Add {U} or {B}.
{2}{U}{B}: Until end of turn, this land becomes a 4/4 blue and black Shark creature with deathtouch. It's still a land.
Whenever this land attacks, target player mills four cards.

Duress

Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.

Soul-Guide Lantern

When this artifact enters, exile target card from a graveyard.
{T}, Sacrifice this artifact: Exile each opponent's graveyard.
{1}, {T}, Sacrifice this artifact: Draw a card.

Singularity Rupture

Destroy all creatures, then any number of target players each mill half their library, rounded down.

Depressurize

Target creature gets -3/-0 until end of turn. Then if that creature's power is 0 or less, destroy it.

The Mindskinner

The Mindskinner can't be blocked.
If a source you control would deal damage to an opponent, prevent that damage and each opponent mills that many cards.

Island

Watery Grave

({T}: Add {U} or {B}.)
As this land enters, you may pay 2 life. If you don't, it enters tapped.

Ghost Vacuum

{T}: Exile target card from a graveyard.
{6}, {T}, Sacrifice this artifact: Put each creature card exiled with this artifact onto the battlefield under your control with a flying counter on it. Each of them is a 1/1 Spirit in addition to its other types. Activate only as a sorcery.

Consuming Aberration

Consuming Aberration's power and toughness are each equal to the number of cards in your opponents' graveyards.
Whenever you cast a spell, each opponent reveals cards from the top of their library until they reveal a land card, then puts those cards into their graveyard.

Gloomlake Verge

{T}: Add {U}.
{T}: Add {B}. Activate only if you control an Island or a Swamp.

Riverchurn Monument

{1}, {T}: Any number of target players each mill two cards. (Each of them puts the top two cards of their library into their graveyard.)
Exhaust — {2}{U}{U}, {T}: Any number of target players each mill cards equal to the number of cards in their graveyard. (Activate each exhaust ability only once.)

The Water Crystal

Blue spells you cast cost {1} less to cast.
If an opponent would mill one or more cards, they mill that many cards plus four instead.
{4}{U}{U}, {T}: Each opponent mills cards equal to the number of cards in your hand.

Unravel

Counter target spell. If the amount of mana spent to cast that spell was less than its mana value, you draw a card.

Undercity Sewers

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

Stock Up

Look at the top five cards of your library. Put two of them into your hand and the rest on the bottom of your library in any order.

Oildeep Gearhulk

Lifelink, ward {1}
When this creature enters, look at target player's hand. You may choose a card from it. If you do, that player discards that card, then draws a card.

Aetherize

Return all attacking creatures to their owner's hand.

Annul

Counter target artifact or enchantment spell.

Negate

Swamp

Refute

Counter target spell. Draw a card, then discard a card.

Shoot the Sheriff

Destroy target non-outlaw creature. (Assassins, Mercenaries, Pirates, Rogues, and Warlocks are outlaws. Everyone else is fair game.)