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.)

Brinebarrow Intruder

Flash
When Brinebarrow Intruder enters, target creature an opponent controls gets -2/-0 until end of turn.

Mana Leak

Counter target spell unless its controller pays {3}.

Duress

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

Village Rites

As an additional cost to cast this spell, sacrifice a creature.
Draw two cards.

Thorn of the Black Rose

Deathtouch
When Thorn of the Black Rose enters, you become the monarch.

Sedraxis Alchemist

When Sedraxis Alchemist enters, if you control a blue permanent, return target nonland permanent to its owner's hand.

Deadly Dispute

As an additional cost to cast this spell, sacrifice an artifact or creature.
Draw two cards and create a Treasure token. (It's an artifact with "{T}, Sacrifice this artifact: Add one mana of any color.")

Mukotai Ambusher

Ninjutsu {1}{B} ({1}{B}, Return an unblocked attacker you control to hand: Put this card onto the battlefield from your hand tapped and attacking.)
Lifelink

Mire Triton

Deathtouch
When Mire Triton enters, mill two cards and you gain 2 life. (To mill a card, put the top card of your library into your graveyard.)

Agony Warp

Target creature gets -3/-0 until end of turn.
Target creature gets -0/-3 until end of turn.

Spy Network

Look at target player's hand, the top card of that player's library, and any face-down creatures they control. Look at the top four cards of your library, then put them back in any order.

Wretched Banquet

Destroy target creature if it has the least power or is tied for least power among creatures on the battlefield.

Curfew

Each player returns a creature they control to its owner's hand.

Shrieking Drake

Flying
When Shrieking Drake enters, return a creature you control to its owner's hand.

Saiba Cryptomancer

Flash
Backup 1 (When this creature enters, put a +1/+1 counter on target creature. If that's another creature, it gains the following ability until end of turn.)
Hexproof

Dusk Legion Zealot

When Dusk Legion Zealot enters, you draw a card and you lose 1 life.

Snuff Out

If you control a Swamp, you may pay 4 life rather than pay this spell's mana cost.
Destroy target nonblack creature. It can't be regenerated.

Peek

Look at target player's hand.
Draw a card.

Brainstorm

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