Urborg, Tomb of Yawgmoth

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

Skithiryx, the Blight Dragon

Flying
Infect (This creature deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
{B}: Skithiryx, the Blight Dragon gains haste until end of turn.
{B}{B}: Regenerate Skithiryx.

Solemn Simulacrum

When Solemn Simulacrum enters, you may search your library for a basic land card, put that card onto the battlefield tapped, then shuffle.
When Solemn Simulacrum dies, you may draw a card.

Vampiric Tutor

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

Geometric Nexus

Whenever a player casts an instant or sorcery spell, put a number of charge counters on Geometric Nexus equal to that spell's mana value.
{6}, {T}, Remove all charge counters from Geometric Nexus: Create a 0/0 green and blue Fractal creature token. Put X +1/+1 counters on it, where X is the number of charge counters removed this way.

Infernal Reckoning

Exile target colorless creature. You gain life equal to its power.

Sudden Edict

Split second (As long as this spell is on the stack, players can't cast spells or activate abilities that aren't mana abilities.)
Target player sacrifices a creature.

Soul Transfer

Choose one. If you control an artifact and an enchantment as you cast this spell, you may choose both instead.
• Exile target creature or planeswalker.
• Return target creature or planeswalker card from your graveyard to your hand.

Diabolic Tutor

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

Dark Petition

Search your library for a card, put that card into your hand, then shuffle.
Spell mastery — If there are two or more instant and/or sorcery cards in your graveyard, add {B}{B}{B}.

Jet Medallion

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

Fateful Handoff

Draw cards equal to the mana value of target artifact or creature you control. An opponent gains control of that permanent.

Swiftfoot Boots

Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control.)
Equip {1}

Sorin Markov

+2: Sorin Markov deals 2 damage to any target and you gain 2 life.
−3: Target opponent's life total becomes 10.
−7: You control target player during that player's next turn.

Cabal Coffers

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

Nykthos, Shrine to Nyx

{T}: Add {C}.
{2}, {T}: Choose a color. Add an amount of mana of that color equal to your devotion to that color. (Your devotion to a color is the number of mana symbols of that color in the mana costs of permanents you control.)

Demonic Bargain

Exile the top thirteen cards of your library, then search your library for a card. Put that card into your hand, then shuffle.

Insatiable Avarice

Spree (Choose one or more additional costs.)
+ {2} — Search your library for a card, then shuffle and put that card on top.
+ {B}{B} — Target player draws three cards and loses 3 life.

Underworld Connections

Enchant land
Enchanted land has "{T}, Pay 1 life: Draw a card."

Coveted Prize

This spell costs {1} less to cast for each creature in your party. (Your party consists of up to one each of Cleric, Rogue, Warrior, and Wizard.)
Search your library for a card, put it into your hand, then shuffle. If you have a full party, you may cast a spell with mana value 4 or less from your hand without paying its mana cost.

Painful Quandary

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

Silence the Believers

Strive — This spell costs {2}{B} more to cast for each target beyond the first.
Exile any number of target creatures and all Auras attached to them.

Wight

Wight enters tapped.
Life Drain — Whenever a creature dealt damage by Wight this turn dies, create a tapped 2/2 black Zombie creature token and exile that card.

Astarion's Thirst

Exile target creature. Put X +1/+1 counters on a commander creature you control, where X is the power of the creature exiled this way.

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}.