Rain of Filth

Until end of turn, lands you control gain "Sacrifice this land: Add {B}."

Arcane Signet

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

Ashiok, Wicked Manipulator

If you would pay life while your library has at least that many cards in it, exile that many cards from the top of your library instead.
+1: Look at the top two cards of your library. Exile one of them and put the other into your hand.
−2: Create two 1/1 black Nightmare creature tokens with "At the beginning of combat on your turn, if a card was put into exile this turn, put a +1/+1 counter on this creature."
−7: Target player exiles the top X cards of their library, where X is the total mana value of cards you own in exile.

Blood Pet

Charcoal Diamond

Charcoal Diamond enters tapped.
{T}: Add {B}.

Vesper Ghoul

{T}, Pay 1 life: Add one mana of any color.

Bubbling Muck

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

Bond of Agony

As an additional cost to cast this spell, pay X life.
Each other player loses X life.

Swamp

Luxior, Giada's Gift

Equipped creature gets +1/+1 for each counter on it.
Equipped permanent isn't a planeswalker and is a creature in addition to its other types. (Loyalty abilities can still be activated.)
Equip planeswalker {1}
Equip {3}

Everflowing Chalice

Multikicker {2} (You may pay an additional {2} any number of times as you cast this spell.)
Everflowing Chalice enters with a charge counter on it for each time it was kicked.
{T}: Add {C} for each charge counter on Everflowing Chalice.