Whisper Agent

Flash
When Whisper Agent enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Cunning Nightbonder

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

Dimir Guildgate

Dimir Guildgate enters tapped.
{T}: Add {U} or {B}.

Voracious Greatshark

Flash
When Voracious Greatshark enters, counter target artifact or creature spell.

Swamp

Thieves' Guild Enforcer

Flash
Whenever Thieves' Guild Enforcer or another Rogue you control enters, each opponent mills two cards.
As long as an opponent has eight or more cards in their graveyard, Thieves' Guild Enforcer gets +2/+1 and has deathtouch.

Island

Castle Locthwain

Castle Locthwain enters tapped unless you control a Swamp.
{T}: Add {B}.
{1}{B}{B}, {T}: Draw a card, then you lose life equal to the number of cards in your hand.

Spectral Sailor

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

Faerie Vandal

Flash
Flying
Whenever you draw your second card each turn, put a +1/+1 counter on Faerie Vandal.

Wavebreak Hippocamp

Whenever you cast your first spell during each opponent's turn, draw a card.

Dismal Backwater

Dismal Backwater enters tapped.
When Dismal Backwater enters, you gain 1 life.
{T}: Add {U} or {B}.

Faerie Duelist

Flash
Flying
When Faerie Duelist enters, target creature an opponent controls gets -2/-0 until end of turn.

Ashiok's Erasure

Flash
When Ashiok's Erasure enters, exile target spell.
Your opponents can't cast spells with the same name as the exiled card.
When Ashiok's Erasure leaves the battlefield, return the exiled card to its owner's hand.

Slitherwisp

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