Seal of Doom

Sacrifice Seal of Doom: Destroy target nonblack creature. It can't be regenerated.

Undead Warchief

Zombie spells you cast cost {1} less to cast.
Zombie creatures you control get +2/+1.

Spiteful Returned

Bestow {3}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Whenever Spiteful Returned or enchanted creature attacks, defending player loses 2 life.
Enchanted creature gets +1/+1.

Underworld Connections

Enchant land
Enchanted land has "{T}, Pay 1 life: Draw a card."

Font of Return

{3}{B}, Sacrifice Font of Return: Return up to three target creature cards from your graveyard to your hand.

Lord of the Accursed

Other Zombies you control get +1/+1.
{1}{B}, {T}: All Zombies gain menace until end of turn.

Tymaret Calls the Dead

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Mill three cards. Then you may exile a creature or enchantment card from your graveyard. If you do, create a 2/2 black Zombie creature token.
III — You gain X life and scry X, where X is the number of Zombies you control.

Gonti's Machinations

Whenever you lose life for the first time each turn, you get {E}. (You get an energy counter. Damage causes loss of life.)
Pay {E}{E}, Sacrifice Gonti's Machinations: Each opponent loses 3 life. You gain life equal to the life lost this way.

Endless Ranks of the Dead

At the beginning of your upkeep, create X 2/2 black Zombie creature tokens, where X is half the number of Zombies you control, rounded down.

Grim Guardian

Constellation — Whenever Grim Guardian or another enchantment you control enters, each opponent loses 1 life.

Meteor Golem

When this creature enters, destroy target nonland permanent an opponent controls.

Deadly Designs

{2}: Put a plot counter on Deadly Designs. Any player may activate this ability.
When there are five or more plot counters on Deadly Designs, sacrifice it. If you do, destroy up to two target creatures.

Doomwake Giant

Constellation — Whenever Doomwake Giant or another enchantment you control enters, creatures your opponents control get -1/-1 until end of turn.

Arvinox, the Mind Flail

Arvinox, the Mind Flail isn't a creature unless you control three or more permanents you don't own.
At the beginning of your end step, exile the bottom card of each opponent's library face down. For as long as those cards remain exiled, you may look at them, you may cast permanent spells from among them, and you may spend mana as though it were mana of any color to cast those spells.

Vessel of Malignity

{1}{B}, Sacrifice Vessel of Malignity: Target opponent exiles two cards from their hand. Activate only as a sorcery.

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.

Curse of Disturbance

Enchant player
Whenever enchanted player is attacked, create a 2/2 black Zombie creature token. Each opponent attacking that player does the same.

The Eldest Reborn

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Each opponent sacrifices a creature or planeswalker of their choice.
II — Each opponent discards a card.
III — Put target creature or planeswalker card from a graveyard onto the battlefield under your control.

Vile Requiem

At the beginning of your upkeep, you may put a verse counter on Vile Requiem.
{1}{B}, Sacrifice Vile Requiem: Destroy up to X target nonblack creatures, where X is the number of verse counters on Vile Requiem. They can't be regenerated.

Fleshbag Marauder

When Fleshbag Marauder enters, each player sacrifices a creature of their choice.

Baleful Eidolon

Bestow {4}{B} (If you cast this card for its bestow cost, it's an Aura spell with enchant creature. It becomes a creature again if it's not attached to a creature.)
Deathtouch (Any amount of damage this deals to a creature is enough to destroy it.)
Enchanted creature gets +1/+1 and has deathtouch.

Grave Peril

When a nonblack creature enters, sacrifice Grave Peril. If you do, destroy that creature.

Thoughtrender Lamia

Constellation — Whenever Thoughtrender Lamia or another enchantment you control enters, each opponent discards a card.

Infernal Tribute

{2}, Sacrifice a nontoken permanent: Draw a card.

Death Baron

Skeletons you control and other Zombies you control get +1/+1 and have deathtouch. (Any amount of damage they deal to a creature is enough to destroy it.)

Ayara, First of Locthwain

Whenever Ayara, First of Locthwain 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.

Agent of Erebos

Constellation — Whenever Agent of Erebos or another enchantment you control enters, exile target player's graveyard.

Crypt Ghast

Extort (Whenever you cast a spell, you may pay {W/B}. If you do, each opponent loses 1 life and you gain that much life.)
Whenever you tap a Swamp for mana, add an additional {B}.

Blood Funnel

Noncreature spells you cast cost {2} less to cast.
Whenever you cast a noncreature spell, counter that spell unless you sacrifice a creature.

Festering Evil

At the beginning of your upkeep, Festering Evil deals 1 damage to each creature and each player.
{B}{B}, Sacrifice Festering Evil: It deals 3 damage to each creature and each player.

Dead Man's Chest

Enchant creature an opponent controls
When enchanted creature dies, exile cards equal to its power from the top of its owner's library. You may cast spells from among those cards for as long as they remain exiled, and mana of any type can be spent to cast them.

Mindwrack Harpy

Flying
At the beginning of combat on your turn, each player mills three cards.

Aphemia, the Cacophony

Flying
At the beginning of your end step, you may exile an enchantment card from your graveyard. If you do, create a 2/2 black Zombie creature token.

Coils of the Medusa

Enchant creature
Enchanted creature gets +1/-1.
Sacrifice Coils of the Medusa: Destroy all non-Wall creatures blocking enchanted creature.

Grave Titan

Deathtouch
Whenever Grave Titan enters or attacks, create two 2/2 black Zombie creature tokens.

Gray Merchant of Asphodel

When Gray Merchant of Asphodel 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.)

Animate Dead

Enchant creature card in a graveyard
When Animate Dead enters, if it's on the battlefield, it loses "enchant creature card in a graveyard" and gains "enchant creature put onto the battlefield with Animate Dead." Return enchanted creature card to the battlefield under your control and attach Animate Dead to it. When Animate Dead leaves the battlefield, that creature's controller sacrifices it.
Enchanted creature gets -1/-0.

Nightmare Shepherd

Flying
Whenever another nontoken creature you control dies, you may exile it. If you do, create a token that's a copy of that creature, except it's 1/1 and it's a Nightmare in addition to its other types.