In the Manga, the key is depicted to be an ordinary golden key with the crest of the Lion, a small circle with a "tail" sprouting out of the top and curling towards the left, stamped on its bow. In the Anime, the key is still depicted as gold but is designed more intricately. The bow of the key is sculpted similar to a lion's head, with the face on the bow's base, complete with two fangs facing downward. The center of the bow is a white arc with the crest of the Lion, colored in dark orange, and surrounded by the lion's "mane". The end of the key's blade is similar to a lion's tail with a crescent moon at the tip.
While in possession of the key, a Celestial Spirit Mage may be able to summon the Lion Leo by reciting the quote, "Open, Gate of the Lion! Leo!". This summons Leo, an expert combatant who employs the Light Magic, Regulus.