Swamp

Dread Return

Return target creature card from your graveyard to the battlefield.
Flashback—Sacrifice three creatures. (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Clawing Torment

Enchant artifact or creature
As long as enchanted permanent is a creature, it gets -1/-1 and can't block.
Enchanted permanent has "At the beginning of your upkeep, you lose 1 life."

Leechridden Swamp

({T}: Add {B}.)
This land enters tapped.
{B}, {T}: Each opponent loses 1 life. Activate only if you control two or more black permanents.

Trespasser's Curse

Enchant player
Whenever a creature enchanted player controls enters, that player loses 1 life and you gain 1 life.

Doomed Dissenter

When this creature dies, create a 2/2 black Zombie creature token.

Macabre Waltz

Return up to two target creature cards from your graveyard to your hand, then discard a card.

Gluttonous Zombie

Fear (This creature can't be blocked except by artifact creatures and/or black creatures.)

Mogis's Marauder

When this creature enters, up to X target creatures each gain intimidate and haste until end of turn, where X is your devotion to black. (A creature with intimidate can't be blocked except by artifact creatures and/or creatures that share a color with it. Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Tymaret, Chosen from Death

Tymaret's toughness is equal to your devotion to black. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)
{1}{B}: Exile up to two target cards from graveyards. You gain 1 life for each creature card exiled this way.

Shamble Back

Exile target creature card from a graveyard. Create a 2/2 black Zombie creature token. You gain 2 life.

Black Dragon

Flying
Acid Breath — When this creature enters, target creature an opponent controls gets -3/-3 until end of turn.

Fell Stinger

Deathtouch
Exploit (When this creature enters, you may sacrifice a creature.)
When this creature exploits a creature, target player draws two cards and loses 2 life.

Echo of Death's Wail

Flying, haste
When this creature enters, gain control of all Rat tokens.
Whenever this creature attacks, you may sacrifice another creature. If you do, draw a card.

Tribute to Horobi

(As this Saga enters and after your draw step, add a lore counter.)
I, II — Each opponent creates a 1/1 black Rat Rogue creature token.
III — Exile this Saga, then return it to the battlefield transformed under your control.

Tribute to Horobi // Echo of Death's Wail

Dark Betrayal

Shadow Alley Denizen

Whenever another black creature you control enters, target creature gains intimidate until end of turn. (It can't be blocked except by artifact creatures and/or creatures that share a color with it.)

Corrupt

Corrupt deals damage to any target equal to the number of Swamps you control. You gain life equal to the damage dealt this way.

Nightmare

Flying (This creature can't be blocked except by creatures with flying or reach.)
Nightmare's power and toughness are each equal to the number of Swamps you control.

Eater of Hope

Flying
{B}, Sacrifice another creature: Regenerate this creature.
{2}{B}, Sacrifice two other creatures: Destroy target creature.

Rat Out

Up to one target creature gets -1/-1 until end of turn. You create a 1/1 black Rat creature token with "This token can't block."

Supernatural Stamina

Until end of turn, target creature gets +2/+0 and gains "When this creature dies, return it to the battlefield tapped under its owner's control."

Ob Nixilis of the Black Oath

+2: Each opponent loses 1 life. You gain life equal to the life lost this way.
−2: Create a 5/5 black Demon creature token with flying. You lose 2 life.
−8: You get an emblem with "{1}{B}, Sacrifice a creature: You gain X life and draw X cards, where X is the sacrificed creature's power."
Ob Nixilis of the Black Oath can be your commander.

Bat Whisperer

When this creature enters, if an opponent lost life this turn, create a 1/1 black Bat creature token with flying.

Maalfeld Twins

When this creature dies, create two 2/2 black Zombie creature tokens.

Bladebrand

Target creature gains deathtouch until end of turn.
Draw a card.

Echo of Dusk

Descend 4 — As long as there are four or more permanent cards in your graveyard, this creature gets +1/+1 and has lifelink.

Locthwain Paladin

Menace (This creature can't be blocked except by two or more creatures.)
Adamant — If at least three black mana was spent to cast this spell, this creature enters with a +1/+1 counter on it.

Awoken Demon

Ecstatic Awakener

{2}{B}, Sacrifice another creature: Draw a card, then transform this creature. Activate only once each turn.

Ecstatic Awakener // Awoken Demon

Squelching Leeches

Squelching Leeches's power and toughness are each equal to the number of Swamps you control.

Jet Medallion

Black spells you cast cost {1} less to cast.

Thrill-Kill Assassin

Deathtouch
Unleash (You may have this creature enter with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.)

Murder

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.)

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.)

Sanguimancy

You draw X cards and you lose X life, where X is your devotion to black. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)

Rot-Tide Gargantua

Exploit (When this creature enters, you may sacrifice a creature.)
When this creature exploits a creature, each opponent sacrifices a creature of their choice.

Ayara, First of Locthwain

Whenever Ayara or another black creature you control enters, each opponent loses 1 life and you gain 1 life.
{T}, Sacrifice another black creature: Draw a card.

Ob Nixilis's Cruelty

Target creature gets -5/-5 until end of turn. If that creature would die this turn, exile it instead.