Marshmist Titan

This spell costs {X} less to cast, where X is your devotion to black. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

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.

Oubliette

When this enchantment enters, target creature phases out until this enchantment leaves the battlefield. Tap that creature as it phases in this way. (Auras and Equipment phase out with it. While permanents are phased out, they're treated as though they don't exist.)

Order of the Ebon Hand

Protection from white
{B}: This creature gains first strike until end of turn.
{B}{B}: This creature gets +1/+0 until end of turn.

Cast Down

Street Wraith

Swampwalk (This creature can't be blocked as long as defending player controls a Swamp.)
Cycling—Pay 2 life. (Pay 2 life, Discard this card: Draw a card.)

Faceless Butcher

When this creature enters, exile another target creature.
When this creature leaves the battlefield, return the exiled card to the battlefield under its owner's control.

Exhume

Each player puts a creature card from their graveyard onto the battlefield.

Troll of Khazad-dûm

This creature can't be blocked except by three or more creatures.
Swampcycling {1} ({1}, Discard this card: Search your library for a Swamp card, reveal it, put it into your hand, then shuffle.)

Faerie Macabre

Flying
Discard this card: Exile up to two target cards from graveyards.

Witch's Cottage

({T}: Add {B}.)
This land enters tapped unless you control three or more other Swamps.
When this land enters untapped, you may put target creature card from your graveyard on top of your library.

Deathgreeter

Whenever another creature dies, you may gain 1 life.

Swamp

Executioner's Capsule

{1}{B}, {T}, Sacrifice this artifact: Destroy target nonblack creature.

Grim Bauble

When this artifact enters, target creature an opponent controls gets -2/-2 until end of turn.
{2}{B}, {T}, Sacrifice this artifact: Surveil 2. (Look at the top two cards of your library, then put any number of them into your graveyard and the rest on top of your library in any order.)

Arms of Hadar

Creatures target player controls get -2/-2 until end of turn.

Hopeless Nightmare

When this enchantment enters, each opponent discards a card and loses 2 life.
When this enchantment is put into a graveyard from the battlefield, scry 2.
{2}{B}: Sacrifice this enchantment.

Gray Merchant of Asphodel

When this creature enters, each opponent loses X life, where X is your devotion to black. You gain life equal to the life lost this way. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Merrow Bonegnawer

{T}: Target player exiles a card from their graveyard.
Whenever you cast a black spell, you may untap this creature.

Consuming Sepulcher

At the beginning of your upkeep, each opponent loses 1 life and you gain 1 life.

Tithing Blade

When this artifact enters, each opponent sacrifices a creature of their choice.
Craft with creature {4}{B} ({4}{B}, Exile this artifact, Exile a creature you control or a creature card from your graveyard: Return this card transformed under its owner's control. Craft only as a sorcery.)