Cabal Ritual

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

Troll of Khazad-dûm

Troll of Khazad-dûm can't be blocked except by three or more creatures.
Swampcycling {1} ({1}, Discard this card: Search your library for a Swamp card, reveal it, put it into your hand, then shuffle.)

Simian Spirit Guide

Exile Simian Spirit Guide from your hand: Add {R}.

Manamorphose

Add two mana in any combination of colors.
Draw a card.

Dark Ritual

Lotus Petal

{T}, Sacrifice Lotus Petal: Add one mana of any color.

Mountain

Exhume

Each player puts a creature card from their graveyard onto the battlefield.

Desperate Ritual

Add {R}{R}{R}.
Splice onto Arcane {1}{R} (As you cast an Arcane spell, you may reveal this card from your hand and pay its splice cost. If you do, add this card's effects to that spell.)

Oliphaunt

Trample
Whenever Oliphaunt attacks, another target creature you control gets +2/+0 and gains trample until end of turn.
Mountaincycling {1} ({1}, Discard this card: Search your library for a Mountain card, reveal it, put it into your hand, then shuffle.)

Pyretic Ritual

Rite of Flame

Add {R}{R}, then add {R} for each card named Rite of Flame in each graveyard.

Vault of Whispers

Great Furnace

Dread Return

Return target creature card from your graveyard to the battlefield.
Flashback—Sacrifice three creatures. (You may cast this card from your graveyard for its flashback cost. Then exile it.)