MAGIC: THE GATHERING
Convoke (Each creature you tap while casting this spell pays for or one mana of that creature's color.)
Search your library for a creature card with converted mana cost X or less and put it into play. Then shuffle your library.
Chord of Calling is a staple of creature-based combo decks. In Modern, it was the namesake of "Kiki-Chord" decks and also sees play in Elves; it's also a great option for any green Commander deck that needs a creature tutor.