Sweep the Skies

Converge — Create a 1/1 colorless Thopter artifact creature token with flying for each color of mana spent to cast this spell.

Expel from Orazca

Ascend (If you control ten or more permanents, you get the city's blessing for the rest of the game.)
Return target nonland permanent to its owner's hand. If you have the city's blessing, you may put that permanent on top of its owner's library instead.

Academy Loremaster

At the beginning of each player's draw step, that player may draw an additional card. If they do, spells they cast this turn cost {2} more to cast.

Kaleidoscorch

Converge — Kaleidoscorch deals X damage to any target, where X is the number of colors of mana spent to cast this spell.
Flashback {4}{R} (You may cast this card from your graveyard for its flashback cost. Then exile it.)

Exert Influence

Converge — Gain control of target creature if its power is less than or equal to the number of colors of mana spent to cast this spell.

Volcanic Island

Jeleva, Nephalia's Scourge

Flying
When Jeleva, Nephalia's Scourge enters, each player exiles the top X cards of their library, where X is the amount of mana spent to cast Jeleva.
Whenever Jeleva attacks, you may cast an instant or sorcery spell from among cards exiled with Jeleva without paying its mana cost.

Brilliant Spectrum

Converge — Draw X cards, where X is the number of colors of mana spent to cast this spell. Then discard two cards.

Chromatic Lantern

Lands you control have "{T}: Add one mana of any color."
{T}: Add one mana of any color.

Lodestone Golem

Nonartifact spells cost {1} more to cast.

Painful Truths

Converge — You draw X cards and you lose X life, where X is the number of colors of mana spent to cast this spell.

Badlands

Sphere of Resistance

Underground Sea

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}.

Cabal Coffers

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

Radiant Epicure

Converge — When Radiant Epicure enters, each opponent loses X life and you gain X life, where X is the number of colors of mana spent to cast this spell.

Urborg, Tomb of Yawgmoth

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

Crystalline Crawler

Converge — Crystalline Crawler enters with a +1/+1 counter on it for each color of mana spent to cast it.
Remove a +1/+1 counter from Crystalline Crawler: Add one mana of any color.
{T}: Put a +1/+1 counter on Crystalline Crawler.

Mana Confluence

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

Radiant Flames

Converge — Radiant Flames deals X damage to each creature, where X is the number of colors of mana spent to cast this spell.