Call to the Netherworld

Return target black creature card from your graveyard to your hand.
Madness {0} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Faith of the Devoted

Whenever you cycle or discard a card, you may pay {1}. If you do, each opponent loses 2 life and you gain 2 life.

Dark Withering

Destroy target nonblack creature.
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.)

Asmoranomardicadaistinaculdacar

As long as you've discarded a card this turn, you may pay {B/R} to cast this spell.
When Asmoranomardicadaistinaculdacar enters, you may search your library for a card named The Underworld Cookbook, reveal it, put it into your hand, then shuffle.
Sacrifice two Foods: Target creature deals 6 damage to itself.

From Under the Floorboards

Madness {X}{B}{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.)
Create three tapped 2/2 black Zombie creature tokens and you gain 3 life. If this spell's madness cost was paid, instead create X of those tokens and you gain X life.

Archfiend of Ifnir

Flying
Whenever you cycle or discard another card, put a -1/-1 counter on each creature your opponents control.
Cycling {2} ({2}, Discard this card: Draw a card.)

Alchemist's Greeting

Alchemist's Greeting deals 4 damage to target creature.
Madness {1}{R} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Abandon Reason

Up to two target creatures each get +1/+0 and gain first strike until end of turn. (They deal combat damage before creatures without first strike.)
Madness {1}{R} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Lembas

When Lembas enters, scry 1, then draw a card.
{2}, {T}, Sacrifice Lembas: You gain 3 life.
When Lembas is put into a graveyard from the battlefield, its owner shuffles it into their library.

Shadow of the Grave

Return to your hand all cards in your graveyard that you cycled or discarded this turn.

Currency Converter

Whenever you discard a card, you may exile that card from your graveyard.
{2}, {T}: Draw a card, then discard a card.
{T}: Put a card exiled with Currency Converter into your graveyard. If it's a land card, create a Treasure token. If it's a nonland card, create a 2/2 black Rogue creature token.

Alms of the Vein

Target opponent loses 3 life and you gain 3 life.
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.)

Chainer, Dementia Master

All Nightmares get +1/+1.
{B}{B}{B}, Pay 3 life: Put target creature card from a graveyard onto the battlefield under your control. That creature is black and is a Nightmare in addition to its other creature types.
When Chainer, Dementia Master leaves the battlefield, exile all Nightmares.

Bone Miser

Whenever you discard a creature card, create a 2/2 black Zombie creature token.
Whenever you discard a land card, add {B}{B}.
Whenever you discard a noncreature, nonland card, draw a card.

Rapacious Guest

Menace
Whenever one or more creatures you control deal combat damage to a player, create a Food token.
Whenever you sacrifice a Food, put a +1/+1 counter on Rapacious Guest.
When Rapacious Guest leaves the battlefield, target opponent loses life equal to its power.

Shadowgrange Archfiend

When Shadowgrange Archfiend enters, each opponent sacrifices a creature with the greatest power among creatures they control. You gain life equal to the greatest power among creatures sacrificed this way.
Madness—{2}{B}, Pay 8 life. (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Necrogoyf

Necrogoyf's power is equal to the number of creature cards in all graveyards.
At the beginning of each player's upkeep, that player discards a card.
Madness {1}{B}{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.)

Anje Falkenrath

Haste
{T}, Discard a card: Draw a card.
Whenever you discard a card, if it has madness, untap Anje Falkenrath.

Glint-Horn Buccaneer

Haste
Whenever you discard a card, Glint-Horn Buccaneer deals 1 damage to each opponent.
{1}{R}, Discard a card: Draw a card. Activate only if Glint-Horn Buccaneer is attacking.

Terminal Agony

Destroy target creature.
Madness {B}{R} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Curse of Fool's Wisdom

Enchant player
Whenever enchanted player draws a card, they lose 2 life and you gain 2 life.
Madness {3}{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.)

Tectonic Reformation

Each land card in your hand has cycling {R}.
Cycling {2} ({2}, Discard this card: Draw a card.)

Containment Construct

Whenever you discard a card, you may exile that card from your graveyard. If you do, you may play that card this turn.

Chainer, Nightmare Adept

Discard a card: You may cast a creature spell from your graveyard this turn. Activate only once each turn.
Whenever a nontoken creature you control enters, if you didn't cast it from your hand, it gains haste until your next turn.

Kitchen Imp

Flying, haste
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.)

Feast of Sanity

Whenever you discard a card, Feast of Sanity deals 1 damage to any target and you gain 1 life.

The Underworld Cookbook

{T}, Discard a card: Create a Food token. (It's an artifact with "{2}, {T}, Sacrifice this artifact: You gain 3 life.")
{4}, {T}, Sacrifice The Underworld Cookbook: Return target creature card from your graveyard to your hand.

Archfiend of Spite

Flying
Whenever a source an opponent controls deals damage to Archfiend of Spite, that source's controller loses that much life unless they sacrifice that many permanents of their choice.
Madness {3}{B}{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.)

Malevolent Whispers

Gain control of target creature until end of turn. Untap that creature. It gets +2/+0 and gains haste until end of turn.
Madness {3}{R} (If you discard this card, discard it into exile. When you do, cast it for its madness cost or put it into your graveyard.)

Tortured Existence

{B}, Discard a creature card: Return target creature card from your graveyard to your hand.