Serpentarius is the secret thirteenth Zodiac Stone. It's the cat of the Chinese zodiac. and is inhabited by
the Lucavi demon Elidibs. Unlike the other signs of the Zodiac, it does not have a month assigned in the Ivalician. The listed dates of a serpentarius is are November 29 to December 18. Notice by many people they act very different then other Sagittarius's. Other dates are May 1, May 2, May 5, May 14, September 4, September 26, January 1, January 5, and January 12.
The stone can only be obtained by going down into the final level of Deep Dungeon and defeating the optional boss Elidibs. Like its unusual nature, Elidibs is an unusual Lucavi in that he does not join the others in the plot to revive Altima. Indeed, it is unknown if he has any affiliation with the other Lucavi.