Brineborn Cutthroat

Flash (You may cast this spell any time you could cast an instant.)
Whenever you cast a spell during an opponent's turn, put a +1/+1 counter on this creature.

Containment Priest

Flash
If a nontoken creature would enter and it wasn't cast, exile it instead.

Island

Aven Mindcensor

Flash
Flying
If an opponent would search a library, that player searches the top four cards of that library instead.

Werefox Bodyguard

Flash
When this creature enters, exile up to one other target non-Fox creature until this creature leaves the battlefield.
{1}{W}, Sacrifice this creature: You gain 2 life.

Slitherwisp

Flash
Whenever you cast another spell that has flash, you draw a card and each opponent loses 1 life.

Spectral Sailor

Flash (You may cast this spell any time you could cast an instant.)
Flying
{3}{U}: Draw a card.

Tyrant's Scorn

Choose one —
• Destroy target creature with mana value 3 or less.
• Return target creature to its owner's hand.

Seachrome Coast

This land enters tapped unless you control two or fewer other lands.
{T}: Add {W} or {U}.

Petty Theft

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

Brazen Borrower

Flash
Flying
This creature can block only creatures with flying.

Brazen Borrower // Petty Theft

Crypt Incursion

Exile all creature cards from target player's graveyard. You gain 3 life for each card exiled this way.

Obscura Interceptor

Flash
Lifelink
When this creature enters, it connives. When it connives this way, return up to one target spell to its owner's hand. (To have a creature connive, draw a card, then discard a card. If you discarded a nonland card, put a +1/+1 counter on that creature.)

Plains

Negate

Ertai Resurrected

Flash
When Ertai Resurrected enters, choose up to one —
• Counter target spell, activated ability, or triggered ability. Its controller draws a card.
• Destroy another target creature or planeswalker. Its controller draws a card.

Cathar Commando

Flash
{1}, Sacrifice this creature: Destroy target artifact or enchantment.

Starlit Mantle

Flash (You may cast this spell any time you could cast an instant.)
Enchant creature you control
When this Aura enters, enchanted creature gains hexproof until end of turn. (It can't be the target of spells or abilities your opponents control.)
Enchanted creature gets +1/+1.

Swamp

Cunning Nightbonder

Flash
Spells with flash you cast cost {1} less to cast and can't be countered.

Grimclimb Pathway

Brightclimb Pathway

Brightclimb Pathway // Grimclimb Pathway

Sunken Hollow

({T}: Add {U} or {B}.)
This land enters tapped unless you control two or more basic lands.

Omen of the Sea

Flash (You may cast this spell any time you could cast an instant.)
When this enchantment enters, scry 2, then draw a card.
{2}{U}, Sacrifice this enchantment: 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.)