Jeweled Lotus

{T}, Sacrifice Jeweled Lotus: Add three mana of any one color. Spend this mana only to cast your commander.

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 Lotus Petal: Add one mana of any color.

Dark Ritual

Songs of the Damned

Add {B} for each creature card in your graveyard.

Command Tower

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

Grist, the Hunger Tide

As long as Grist, the Hunger Tide isn't on the battlefield, it's a 1/1 Insect creature in addition to its other types.
+1: Create a 1/1 black and green Insect creature token, then mill a card. If an Insect card was milled this way, put a loyalty counter on Grist and repeat this process.
−2: You may sacrifice a creature. When you do, destroy target creature or planeswalker.
−5: Each opponent loses life equal to the number of creature cards in your graveyard.

Culling Ritual

Destroy each nonland permanent with mana value 2 or less. Add {B} or {G} for each permanent destroyed this way.