Libra's key is a gold key with a very decorative bow. The center of the bow features the crest of the heavenly scales. The end of the key's blade appears to be a thicker variation of the symbol, also resembling a horseshoe. The derivative of the design of gleaming circles on the sides of the bow and the top of the handle appear to be the pans of scales, which is what Libra utilizes in combat.
While in possession of the key, a Celestial Spirit Mage may be able to summon the Heavenly Scales Libra by reciting the quote, "Open the Gate of the Heavenly Scales! Libra!". This summons Libra, who is able to use Gravity Change, allowing her to alter the gravity surrounding her target(s).