Suq'Ata Assassin

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)
Whenever Suq'Ata Assassin attacks and isn't blocked, defending player gets a poison counter. (A player with ten or more poison counters loses the game.)

Midnight Assassin

Hooded Assassin

When Hooded Assassin enters, choose one —
• Put a +1/+1 counter on Hooded Assassin.
• Destroy target creature that was dealt damage this turn.

Dark Impostor

{4}{B}{B}: Exile target creature and put a +1/+1 counter on Dark Impostor.
Dark Impostor has all activated abilities of all creature cards exiled with it.

Swamp

Restless Dreams

As an additional cost to cast this spell, discard X cards.
Return X target creature cards from your graveyard to your hand.

Stronghold Assassin

{T}, Sacrifice a creature: Destroy target nonblack creature.

Big Game Hunter

When Big Game Hunter enters, destroy target creature with power 4 or greater. It can't be regenerated.
Madness {B} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Thriving Moor

Thriving Moor enters tapped. As it enters, choose a color other than black.
{T}: Add {B} or one mana of the chosen color.

Eyeblight Assassin

When Eyeblight Assassin enters, target creature an opponent controls gets -1/-1 until end of turn.

Royal Assassin

Hired Poisoner

Guildsworn Prowler

Deathtouch
When Guildsworn Prowler dies, if it wasn't blocking, draw a card.

Murder

Mari, the Killing Quill

Whenever a creature an opponent controls dies, exile it with a hit counter on it.
Assassins, Mercenaries, and Rogues you control have deathtouch and "Whenever this creature deals combat damage to a player, you may remove a hit counter from a card that player owns in exile. If you do, draw a card and create two Treasure tokens."