Chord of Calling

Instant, XGGG (3)
Convoke (Each creature you tap while casting this spell reduces its cost by {1} or by one mana of that creature's color.)

Search your library for a creature card with converted mana cost X or less and put it onto the battlefield. Then shuffle your library.¹
Illus. Heather Hudson

Gatherer Card Rulings [Nov 2009]

• 10/1/2005: You announce what X is first, and then announce which creatures you're tapping to reduce the cost to cast the spell.

Format Legality	Legal in Vintage, Legacy, Extended, MTGO Classic Banned in Standard
Printings (1/9)	Ravnica: City of Guilds (Rare)