Quest for the Nihil Stone

Whenever an opponent discards a card, you may put a quest counter on Quest for the Nihil Stone.
At the beginning of each opponent's upkeep, if that player has no cards in hand and Quest for the Nihil Stone has two or more quest counters on it, you may have that player lose 5 life.

Bandit's Talent

(Gain the next level as a sorcery to add its ability.)
When Bandit's Talent enters, each opponent discards two cards unless they discard a nonland card.
{B}: Level 2
At the beginning of each opponent's upkeep, if that player has one or fewer cards in hand, they lose 2 life.
{3}{B}: Level 3
At the beginning of your draw step, draw an additional card for each opponent who has one or fewer cards in hand.

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.

Gibbering Descent

At the beginning of each player's upkeep, that player loses 1 life and discards a card.
Hellbent — Skip your upkeep step if you have no cards in hand.
Madness {2}{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.)

Megrim

Whenever an opponent discards a card, Megrim deals 2 damage to that player.

Feast of Sanity

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

Hopeless Nightmare

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

Oppression

Whenever a player casts a spell, that player discards a card.

Bottomless Pit

At the beginning of each player's upkeep, that player discards a card at random.

Strands of Undeath

Enchant creature
When Strands of Undeath enters, target player discards two cards.
{B}: Regenerate enchanted creature.

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.

Court of Ambition

When Court of Ambition enters, you become the monarch.
At the beginning of your upkeep, each opponent loses 3 life unless they discard a card. If you're the monarch, instead each opponent loses 6 life unless they discard two cards.

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.

The Cruelty of Gix

Read ahead (Choose a chapter and start with that many lore counters. Add one after your draw step. Skipped chapters don't trigger. Sacrifice after III.)
I — Target opponent reveals their hand. You choose a creature or planeswalker card from it. That player discards that card.
II — Search your library for a card, put that card into your hand, then shuffle. You lose 3 life.
III — Put target creature card from a graveyard onto the battlefield under your control.

Creeping Dread

At the beginning of your upkeep, each player discards a card. Each opponent who discarded a card that shares a card type with the card you discarded loses 3 life. (Players reveal the discarded cards simultaneously.)

Liliana's Caress

Whenever an opponent discards a card, that player loses 2 life.

Discordant Dirge

At the beginning of your upkeep, you may put a verse counter on Discordant Dirge.
{B}, Sacrifice Discordant Dirge: Look at target opponent's hand and choose up to X cards from it, where X is the number of verse counters on Discordant Dirge. That player discards those cards.

Dying Wail

Enchant creature
When enchanted creature dies, target player discards two cards.

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.

Tinybones, Bauble Burglar

Whenever an opponent discards a card, exile it from their graveyard with a stash counter on it.
During your turn, you may play cards you don't own with stash counters on them from exile, and mana of any type can be spent to cast those spells.
{3}{B}, {T}: Each opponent discards a card. Activate only as a sorcery.

Waste Not

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

Raiders' Wake

Whenever an opponent discards a card, that player loses 2 life.
Raid — At the beginning of your end step, if you attacked this turn, target opponent discards a card.

Dying to Serve

Whenever you discard one or more cards, create a tapped 2/2 black Zombie creature token. This ability triggers only once each turn.

Mind Slash

{B}, Sacrifice a creature: Target opponent reveals their hand. You choose a card from it. That player discards that card. Activate only as a sorcery.

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.

Sinister Concoction

{B}, Pay 1 life, Mill a card, Discard a card, Sacrifice Sinister Concoction: Destroy target creature.

Brink of Madness

At the beginning of your upkeep, if you have no cards in hand, sacrifice Brink of Madness and target opponent discards their hand.

Larceny

Whenever a creature you control deals combat damage to a player, that player discards a card.

Tortured Existence

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

Zombie Infestation

Discard two cards: Create a 2/2 black Zombie creature token.

Necrogen Mists

At the beginning of each player's upkeep, that player discards a card.

Honden of Night's Reach

At the beginning of your upkeep, target opponent discards a card for each Shrine you control.

Cloak of Confusion

Enchant creature you control
Whenever enchanted creature attacks and isn't blocked, you may have it assign no combat damage this turn. If you do, defending player discards a card at random.

Painful Quandary

Whenever an opponent casts a spell, that player loses 5 life unless they discard a card.