Celestial Spirit Gate Keys are Magical keys that can be used to summon Celestial Spirits, beings from another dimension that can be used to fight their contractor's opponents, to do chores or just to hang around with. There are two different types of Celestial Spirit Gate Keys: the Silver Keys and the Gold Keys. The Silver Keys are common keys that can be bought from stores while the Gold Keys are very rare keys that can be used to summon the Zodiac Spirits. According to Yukino, it is said that when all twelve Zodiac Keys are gathered, one is able to "open the gate to changing the world".
The Golden keys appear to be more stylized in the anime, appearing with intricately designed bows, handles and blades to the theme of the summoned Spirit, while in the manga they appear as ordinary keys with octagonal shaped bows and respective Constellation's symbol engraved in its center. Recent chapters in the manga depict the keys in their stylized forms, as seen when Lucy summoned Taurus and Scorpio simultaneously or when Yukino offers Lucy her two keys.