Chainer's Torment

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I, II — Chainer's Torment deals 2 damage to each opponent and you gain 2 life.
III — Create an X/X black Nightmare Horror creature token, where X is half your life total, rounded up. It deals X damage to you.

Call of the Nightwing

Create a 1/1 blue and black Horror creature token with flying.
Cipher (Then you may exile this spell card encoded on a creature you control. Whenever that creature deals combat damage to a player, its controller may cast a copy of the encoded card without paying its mana cost.)

Paralyzing Grasp

Enchant creature
Enchanted creature doesn't untap during its controller's untap step.

Elspeth's Nightmare

(As this Saga enters and after your draw step, add a lore counter. Sacrifice after III.)
I — Destroy target creature an opponent controls with power 2 or less.
II — Target opponent reveals their hand. You choose a noncreature, nonland card from it. That player discards that card.
III — Exile target opponent's graveyard.

Mesmeric Fiend

When Mesmeric Fiend enters, target opponent reveals their hand and you choose a nonland card from it. Exile that card.
When Mesmeric Fiend leaves the battlefield, return the exiled card to its owner's hand.

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.

Swimmer in Nightmares

Swimmer in Nightmares gets +3/+0 as long as there are ten or more cards in a single graveyard.
Swimmer in Nightmares can't be blocked as long as you control an Ashiok planeswalker.

Artful Takedown

Choose one or both —
• Tap target creature.
• Target creature gets -2/-4 until end of turn.

Dismal Backwater

This land enters tapped.
When this land enters, you gain 1 life.
{T}: Add {U} or {B}.

Nightmare Void

Target player reveals their hand. You choose a card from it. That player discards that card.
Dredge 2 (If you would draw a card, you may mill two cards instead. If you do, return this card from your graveyard to your hand.)

Nightmarish End

Target creature gets -X/-X until end of turn, where X is the number of cards in your hand.

Plague Mare

Plague Mare can't be blocked by white creatures.
When Plague Mare enters, creatures your opponents control get -1/-1 until end of turn.

Ashiok, Nightmare Muse

+1: Create a 2/3 blue and black Nightmare creature token with "Whenever this creature attacks or blocks, each opponent exiles the top two cards of their library."
−3: Return target nonland permanent to its owner's hand, then that player exiles a card from their hand.
−7: You may cast up to three spells from among face-up cards your opponents own from exile without paying their mana costs.

Psychic Symbiont

Flying
When Psychic Symbiont enters, target opponent discards a card and you draw a card.

Void Beckoner

Deathtouch
Cycling {2}{B} ({2}{B}, Discard this card: Draw a card.)
When you cycle Void Beckoner, put a deathtouch counter on target creature you control.

Devourer of Memory

Whenever one or more cards are put into your graveyard from your library, Devourer of Memory gets +1/+1 until end of turn and can't be blocked this turn.
{1}{U}{B}: Mill a card.

Drown in the Loch

Choose one —
• Counter target spell with mana value less than or equal to the number of cards in its controller's graveyard.
• Destroy target creature with mana value less than or equal to the number of cards in its controller's graveyard.

Tainted Isle

{T}: Add {C}.
{T}: Add {U} or {B}. Activate only if you control a Swamp.

Silumgar's Command

Choose two —
• Counter target noncreature spell.
• Return target permanent to its owner's hand.
• Target creature gets -3/-3 until end of turn.
• Destroy target planeswalker.

Skittering Monstrosity

When you cast a creature spell, sacrifice Skittering Monstrosity.

Ashiok's Skulker

{3}{U}: Ashiok's Skulker can't be blocked this turn.

Faceless Butcher

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

Agonizing Syphon

Agonizing Syphon deals 3 damage to any target and you gain 3 life.

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.

Waking Nightmare

Bad River

Bad River enters tapped.
{T}, Sacrifice Bad River: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

Probe

Kicker {1}{B} (You may pay an additional {1}{B} as you cast this spell.)
Draw three cards, then discard two cards. If this spell was kicked, target player discards two cards.

Laquatus's Champion

When Laquatus's Champion enters, target player loses 6 life.
When Laquatus's Champion leaves the battlefield, that player gains 6 life.
{B}: Regenerate Laquatus's Champion.

Agonizing Remorse

Target opponent reveals their hand. You choose a nonland card from it or a card from their graveyard. Exile that card. You lose 1 life.

Agony Warp

Target creature gets -3/-0 until end of turn.
Target creature gets -0/-3 until end of turn.

Yarok's Fenlurker

When Yarok's Fenlurker enters, each opponent exiles a card from their hand.
{2}{B}: Yarok's Fenlurker gets +1/+1 until end of turn.

Ingenious Skaab

Prowess (Whenever you cast a noncreature spell, this creature gets +1/+1 until end of turn.)
{U}: Ingenious Skaab gets +1/-1 until end of turn.

Notion Rain

Surveil 2, then draw two cards. Notion Rain deals 2 damage to you. (To 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.)

Swamp

Grimdancer

Grimdancer enters with your choice of two different counters on it from among menace, deathtouch, and lifelink.

Submerged Boneyard

Submerged Boneyard enters tapped.
{T}: Add {U} or {B}.

Island

Annihilate

Destroy target nonblack creature. It can't be regenerated.
Draw a card.

Stallion of Ashmouth

Delirium — {1}{B}: Stallion of Ashmouth gets +1/+1 until end of turn. Activate only if there are four or more card types among cards in your graveyard.

Dinrova Horror

When Dinrova Horror enters, return target permanent to its owner's hand, then that player discards a card.