Gate of the Snake Charmer Key

The Gate of the Serpent-Holder Key is a Celestial Spirit Gate Key used by Celestial Spirit Mages to summon the Serpent-Holder, Ophiuchus.

Description
In the Manga, the key is depicted to be an unknown key with the crest of the Serpent-Bearer stamped on its bow.

Usage
While in possession of the key, a Celestial Spirit Mage may be able to summon the Serpent-Holder Ophiuchus by reciting the quote "Open Gate of the Serpent-Holder! Ophiuchus!". This summons Ophiuchus, a machine-like Celestial Spirit.