Hidden Herbalists

Revolt — When Hidden Herbalists enters, if a permanent you controlled left the battlefield this turn, add {G}{G}.

Infernal Plunge

As an additional cost to cast this spell, sacrifice a creature.
Add {R}{R}{R}.

Channel the Suns

Wild Cantor

({R/G} can be paid with either {R} or {G}.)
Sacrifice Wild Cantor: Add one mana of any color.

Inner Fire

Brood Birthing

If you control an Eldrazi Spawn, create three 0/1 colorless Eldrazi Spawn creature tokens. They have "Sacrifice this creature: Add {C}." Otherwise, create one of those tokens.

Open the Omenpaths

Choose one —
• Add two mana of any one color and two mana of any other color. Spend this mana only to cast creature or enchantment spells.
• Creatures you control get +1/+0 until end of turn.

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.)

Seething Song

Mana Seism

Sacrifice any number of lands, then add that much {C}.

Deconstruct

Meeting of the Five

Exile the top ten cards of your library. You may cast spells with exactly three colors from among them this turn. Add {W}{W}{U}{U}{B}{B}{R}{R}{G}{G}. Spend this mana only to cast spells with exactly three colors.

Harnfel, Horn of Bounty

Discard a card: Exile the top two cards of your library. You may play those cards this turn.

Birgi, God of Storytelling

Whenever you cast a spell, add {R}. Until end of turn, you don't lose this mana as steps and phases end.
Creatures you control can boast twice during each of your turns rather than once.

Birgi, God of Storytelling // Harnfel, Horn of Bounty

Vessel of Volatility

{1}{R}, Sacrifice Vessel of Volatility: Add {R}{R}{R}{R}.

Satyr Hedonist

{R}, Sacrifice Satyr Hedonist: Add {R}{R}{R}.

Priest of Urabrask

When Priest of Urabrask enters, add {R}{R}{R}.

Akki Rockspeaker

Dragonrage

Add {R} for each attacking creature you control. Until end of turn, attacking creatures you control gain "{R}: This creature gets +1/+0 until end of turn."

Mana Geyser

Add {R} for each tapped land your opponents control.

Manamorphose

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

Braid of Fire

Cumulative upkeep—Add {R}. (At the beginning of your upkeep, put an age counter on this permanent, then sacrifice it unless you pay its upkeep cost for each age counter on it.)

Irencrag Feat

Add seven {R}. You can cast only one more spell this turn.

Burning-Tree Emissary

When Burning-Tree Emissary enters, add {R}{G}.

Pyretic Ritual

Seasonal Ritual

Add one mana of any color. (Then exile this card. You may cast the creature later from exile.)

Rosethorn Acolyte

Rosethorn Acolyte // Seasonal Ritual

Battle Hymn

Geosurge

Add {R}{R}{R}{R}{R}{R}{R}. Spend this mana only to cast artifact or creature spells.