Have

Devourer of Memory

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

Baleful Strix

Flying, deathtouch
When this creature enters, draw a card.

Inundated Archive

This land enters tapped.
{T}: Add {U} or {B}.

Waterlogged Teachings

Search your library for an instant card or a card with flash, reveal it, put it into your hand, then shuffle.

Waterlogged Teachings // Inundated Archive

Emet-Selch of the Third Seat

Spells you cast from your graveyard cost {2} less to cast.
Whenever one or more opponents lose life, you may cast target instant or sorcery card from your graveyard. If that spell would be put into your graveyard, exile it instead. Do this only once each turn.

Lord of the Nazgûl

Flying
Wraiths you control have protection from Ring-bearers.
Whenever you cast an instant or sorcery spell, create a 3/3 black Wraith creature token with menace. Then if you control nine or more Wraiths, Wraiths you control have base power and toughness 9/9 until end of turn.

Messenger Hawk

Flying
When this creature enters, create a Clue token. (It's an artifact with "{2}, Sacrifice this token: Draw a card.")
This creature gets +2/+0 as long as you've drawn two or more cards this turn.

Artful Takedown

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

Araumi of the Dead Tide

{T}, Exile cards from your graveyard equal to the number of opponents you have: Target creature card in your graveyard gains encore until end of turn. The encore cost is equal to its mana cost. (Exile the creature card and pay its mana cost: For each opponent, create a token copy that attacks that opponent this turn if able. They gain haste. Sacrifice them at the beginning of the next end step. Activate only as a sorcery.)

Polluted Delta

{T}, Pay 1 life, Sacrifice this land: Search your library for an Island or Swamp card, put it onto the battlefield, then shuffle.

Hostage Taker

When this creature enters, exile another target creature or artifact until this creature leaves the battlefield. You may cast that card for as long as it remains exiled, and mana of any type can be spent to cast that spell.

Ancient Excavation

Draw cards equal to the number of cards in your hand, then discard a card for each card drawn this way.
Basic landcycling {2} ({2}, Discard this card: Search your library for a basic land card, reveal it, put it into your hand, then shuffle.)

Oblivion

Aftermath (Cast this spell only from your graveyard. Then exile it.)
Target opponent discards two cards.

Consign

Return target nonland permanent to its owner's hand.

Consign // Oblivion

Foggy Swamp Spirit Keeper

Lifelink
Whenever you draw your second card each turn, create a 1/1 colorless Spirit creature token with "This token can't block or be blocked by non-Spirit creatures."

The Scarab God

At the beginning of your upkeep, each opponent loses X life and you scry X, where X is the number of Zombies you control.
{2}{U}{B}: Exile target creature card from a graveyard. Create a token that's a copy of it, except it's a 4/4 black Zombie.
When The Scarab God dies, return it to its owner's hand at the beginning of the next end step.

Hidetsugu and Kairi

Flying
When Hidetsugu and Kairi enters, draw three cards, then put two cards from your hand on top of your library in any order.
When Hidetsugu and Kairi dies, exile the top card of your library. Target opponent loses life equal to its mana value. If it's an instant or sorcery card, you may cast it without paying its mana cost.

Obsessive Stitcher

{T}: Draw a card, then discard a card.
{2}{U}{B}, {T}, Sacrifice this creature: Return target creature card from your graveyard to the battlefield.

Undercity Sewers

({T}: Add {U} or {B}.)
This land enters tapped.
When this land enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Disinformation Campaign

When this enchantment enters, you draw a card and each opponent discards a card.
Whenever you surveil, return this enchantment to its owner's hand.

Mind Drill Assailant

Threshold — As long as there are seven or more cards in your graveyard, this creature gets +3/+0.
{2}{U/B}: Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Ertai Resurrected

Flash
When Ertai Resurrected enters, choose up to one —
• Counter target spell, activated ability, or triggered ability. Its controller draws a card.
• Destroy another target creature or planeswalker. Its controller draws a card.

Tyrant's Scorn

Choose one —
• Destroy target creature with mana value 3 or less.
• Return target creature to its owner's hand.

Hades, Sorcerer of Eld

Vigilance
Echo of the Lost — During your turn, you may play cards from your graveyard.
If a card or token would be put into your graveyard from anywhere, exile it instead.

Emet-Selch, Unsundered

Vigilance
Whenever Emet-Selch enters or attacks, draw a card, then discard a card.
At the beginning of your upkeep, if there are fourteen or more cards in your graveyard, you may transform Emet-Selch.

Emet-Selch, Unsundered // Hades, Sorcerer of Eld

Dreadwing Scavenger

Flying
Whenever this creature enters or attacks, draw a card, then discard a card.
Threshold — This creature gets +1/+1 and has deathtouch as long as there are seven or more cards in your graveyard.

Sinister Hideout

This land enters tapped.
{T}: Add {U} or {B}.
{4}, {T}: Surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Singularity Rupture

Destroy all creatures, then any number of target players each mill half their library, rounded down.

Lazav, the Multifarious

When Lazav enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)
{X}: Lazav becomes a copy of target creature card in your graveyard with mana value X, except its name is Lazav, the Multifarious, it's legendary in addition to its other types, and it has this ability.

Mirko, Obsessive Theorist

Flying, vigilance
Whenever you surveil, put a +1/+1 counter on Mirko.
At the beginning of your end step, you may return target creature card with power less than Mirko's from your graveyard to the battlefield with a finality counter on it. (If it would die, exile it instead.)

Ultimecia, Omnipotent

Menace (This creature can't be blocked except by two or more creatures.)
Time Compression — When this creature transforms into Ultimecia, Omnipotent, take an extra turn after this one.

Ultimecia, Time Sorceress

Whenever Ultimecia enters or attacks, 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.)
At the beginning of your end step, you may pay {4}{U}{U}{B}{B} and exile eight cards from your graveyard. If you do, transform Ultimecia.

Ultimecia, Time Sorceress // Ultimecia, Omnipotent

Dispersal

Each opponent returns a nonland permanent they control with the greatest mana value among permanents they control to its owner's hand, then discards a card.

Discovery

Surveil 2, then draw a card. (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.)

Discovery // Dispersal

Whisper Agent

Flash
When this creature enters, surveil 1. (Look at the top card of your library. You may put it into your graveyard.)

Dimir Spybug

Flying
Menace (This creature can't be blocked except by two or more creatures.)
Whenever you surveil, put a +1/+1 counter on this creature.

Dihada's Ploy

Draw two cards, then discard a card. You gain life equal to the number of cards you've discarded this turn.
Jump-start (You may cast this card from your graveyard by discarding a card in addition to paying its other costs. Then exile this card.)

Azula, Cunning Usurper

Firebending 2 (Whenever this creature attacks, add {R}{R}. This mana lasts until end of combat.)
When Azula enters, target opponent exiles a nontoken creature they control, then they exile a nonland card from their graveyard.
During your turn, you may cast cards exiled with Azula and you may cast them as though they had flash. Mana of any type can be spent to cast those spells.