Cabal Stronghold

{T}: Add {C}.
{3}, {T}: Add {B} for each basic Swamp you control.

K'rrik, Son of Yawgmoth

({B/P} can be paid with either {B} or 2 life.)
Lifelink
For each {B} in a cost, you may pay 2 life rather than pay that mana.
Whenever you cast a black spell, put a +1/+1 counter on K'rrik.

Tymaret, Chosen from Death

Tymaret's toughness is equal to your devotion to black. (Each {B} in the mana costs of permanents you control counts toward your devotion to black.)
{1}{B}: Exile up to two target cards from graveyards. You gain 1 life for each creature card exiled this way.

Urborg, Tomb of Yawgmoth

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

The Spot's Portal

Put target creature on the bottom of its owner's library. You lose 2 life unless you control a Villain.

Gilded Lotus

Arcane Signet

{T}: Add one mana of any color in your commander's color identity.

Bubbling Muck

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

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}.

Thran Dynamo

Cabal Ritual

Add {B}{B}{B}.
Threshold — Add {B}{B}{B}{B}{B} instead if seven or more cards are in your graveyard.

Lotus Petal

{T}, Sacrifice this artifact: Add one mana of any color.

Arvinox, the Mind Flail

Arvinox isn't a creature unless you control three or more permanents you don't own.
At the beginning of your end step, exile the bottom card of each opponent's library face down. For as long as those cards remain exiled, you may look at them, you may cast permanent spells from among them, and you may spend mana as though it were mana of any color to cast those spells.

Cabal Coffers

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

Sol Ring

Brainstealer Dragon

Flying
At the beginning of your end step, exile the top card of each opponent's library. You may play those cards for as long as they remain exiled. If you cast a spell this way, you may spend mana as though it were mana of any color to cast it.
Whenever a nonland permanent an opponent owns enters the battlefield under your control, they lose life equal to its mana value.

Swamp

Doomwake Giant

Constellation — Whenever this creature or another enchantment you control enters, creatures your opponents control get -1/-1 until end of turn.

Gonti, Lord of Luxury

Deathtouch
When Gonti enters, look at the top four cards of target opponent's library, exile one of them face down, then put the rest on the bottom of that library in a random order. You may cast that card for as long as it remains exiled, and mana of any type can be spent to cast that spell.