Urborg, Tomb of Yawgmoth

Each land is a Swamp in addition to its other land types.

Exsanguinate

Each opponent loses X life. You gain life equal to the life lost this way.

Reanimate

Put target creature card from a graveyard onto the battlefield under your control. You lose life equal to its mana value.

Demonic Tutor

Search your library for a card, put that card into your hand, then shuffle.

Necromancy

You may cast Necromancy as though it had flash. If you cast it any time a sorcery couldn't have been cast, the controller of the permanent it becomes sacrifices it at the beginning of the next cleanup step.
When Necromancy enters, if it's on the battlefield, it becomes an Aura with "enchant creature put onto the battlefield with Necromancy." Put target creature card from a graveyard onto the battlefield under your control and attach Necromancy to it. When Necromancy leaves the battlefield, that creature's controller sacrifices it.

Chains of Mephistopheles

If a player would draw a card except the first one they draw in each of their draw steps, that player discards a card instead. If the player discards a card this way, they draw a card. If the player doesn't discard a card this way, they mill a card.

Wayfarer's Bauble

{2}, {T}, Sacrifice Wayfarer's Bauble: Search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.

Awaken the Erstwhile

Each player discards all the cards in their hand, then creates that many 2/2 black Zombie creature tokens.

Mana Crypt

At the beginning of your upkeep, flip a coin. If you lose the flip, Mana Crypt deals 3 damage to you.
{T}: Add {C}{C}.

Cloak and Dagger

Equipped creature gets +2/+0 and has shroud. (It can't be the target of spells or abilities.)
Whenever a Rogue creature enters, you may attach Cloak and Dagger to it.
Equip {3}

Syphon Mind

Each other player discards a card. You draw a card for each card discarded this way.

Torpor Orb

Creatures entering don't cause abilities to trigger.

Null Rod

Activated abilities of artifacts can't be activated.

Jet Medallion

Black spells you cast cost {1} less to cast.

Mind Twist

Target player discards X cards at random.

Necrogen Mists

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

Fraying Omnipotence

Each player loses half their life, then discards half the cards in their hand, then sacrifices half the creatures they control of their choice. Round up each time.

Smallpox

Each player loses 1 life, discards a card, sacrifices a creature of their choice, then sacrifices a land of their choice.

Mind Rake

Target player discards two cards.
Overload {1}{B} (You may cast this spell for its overload cost. If you do, change "target" in its text to "each.")

Bottomless Pit

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

Hymn to Tourach

Target player discards two cards at random.

Death Cloud

Each player loses X life, discards X cards, sacrifices X creatures of their choice, then sacrifices X lands of their choice.

Dark Ritual

Imp's Mischief

Change the target of target spell with a single target. You lose life equal to that spell's mana value.

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}.

Vicious Rumors

Vicious Rumors deals 1 damage to each opponent. Each opponent discards a card, then mills a card. You gain 1 life.

Each player loses a third of their life, then discards a third of the cards in their hand, then sacrifices a third of the creatures they control of their choice, then sacrifices a third of the lands they control of their choice. Round up each time.

Vampiric Tutor

Search your library for a card, then shuffle and put that card on top. You lose 2 life.

Delirium Skeins

Dark Deal

Each player discards all the cards in their hand, then draws that many cards minus one.

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.

Sol Ring

Lightning Greaves

Equipped creature has haste and shroud. (It can't be the target of spells or abilities.)
Equip {0}

Oppression

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

Words of Waste

{1}: The next time you would draw a card this turn, each opponent discards a card instead.

Mindslicer

When Mindslicer dies, each player discards their hand.

Plaguecrafter

When Plaguecrafter enters, each player sacrifices a creature or planeswalker of their choice. Each player who can't discards a card.

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.

Geth's Grimoire

Whenever an opponent discards a card, you may draw a card.

Arterial Flow

Each opponent discards two cards. If you control a Vampire, each opponent loses 2 life and you gain 2 life.

Deserted Temple

{T}: Add {C}.
{1}, {T}: Untap target land.

Ancient Tomb

{T}: Add {C}{C}. Ancient Tomb deals 2 damage to you.

Cabal Coffers

{2}, {T}: Add {B} for each Swamp you control.

Bubbling Muck

Until end of turn, whenever a player taps a Swamp for mana, that player adds an additional {B}.

Phyrexian Tower

{T}: Add {C}.
{T}, Sacrifice a creature: Add {B}{B}.

Deadly Rollick

If you control a commander, you may cast this spell without paying its mana cost.
Exile target creature.