One of many Stellazzio in the world. "Their future was uncertain, but Scorpio and Virgo kissed in the light of dusk. That moment meant everything."
Ophiuchus, the snake-holder, also known as Serpentarius, is a recurring symbol in Final Fantasy series. Though usually not counted as a Zodiac sign, Ophiuchus is the thirteenth ecliptic constellation, meaning that the sun seems to pass through it during its visible route through the heavens.
Mainstream astrology uses the 12-sign Zodiac, dividing the sky into 12 sectors with each sign corresponding to the location of sun through a star group. The idea of a 13-sign Zodiac is propagated through the publication and promotion of a 1995 book The 13 Signs of the Zodiac by Walter Berg and Mark Yazaki, which was a bestseller in Japan. This explains the appearance of Ophiuchus in Japanese pop culture, especially in the Final Fantasy series. The Zodiac sign of Ophiuchus was designed by Berg.
Ophiuchus is the final Stellazzio coin collected by Queen Stella. After all the other twelve are discovered, Stella begins to suspect that there may be a final, secret one. It is found around the healing spring in Quan's Dwelling, in the same location the Scorpio coin was found.
The Ophiuchus Subligar is one of the thirteen Zodiac subligaria, which can be obtained from a Fomor Beastmaster in specific level-capped dungeons around Tavnazia. It is used to obtain the Gaudy Harness, a light armor worn by Bards and Beastmasters.
Serpentarius is the secret thirteenth Zodiac Stone, and is inhabited by the Lucavi demon Elidibus. Unlike the other signs of the Zodiac, it does not have a month assigned in the Ivalician calendar, and so has no effect on character affinity. All characters simply react neutrally to the one enemy with this sign, Elidibus, regardless of their own Zodiac sign. The stone can only be obtained by going down into the final level of Midlight's Deep and defeating the optional boss Elidibus. Like its unusual nature, Elidibus is an unusual Lucavi in that he does not join the others in the plot to revive Ultima. Indeed, it is unknown if he has any affiliation with the other Lucavi.