The Priestess (Miko, 巫女) is the "girl" who came from another world to summon a beast god in an assigned kingdom. Only virgin maidens can fulfill the role of a priestess. By gathering all of her celestial warriors, she is able to summon her corresponding beast god and is rewarded with the ability to grant three wishes after completing the summoning ceremony.
Ultimately, however, the priestess is a sacrifice to the beast god after she has coupled with him. As she summons the God, her body begins to mutate painfully (both Yui and Takiko experimented pain and scales that grew on their skins) and at the end of the summoning session, she will disappear.
Only Priestesses with a strong enough will survive the ordeal, if not, they are devoured by the god. Once all the wishes have been granted and the god summoned if the priestess survives she must return to her own world, as her mission is over and she cannot remain in the book.
There have also been fake Priestesses, young women from either the world of the book or the real one who take the place of a real priestess for one or another motive. Two of these fake Priestesses are Mayo Sakaki (tricked into becoming a false Priestess of Suzaku by a fake God) and Neiran (willingly usurped the Priestess of Byakko spot to improve her life, which had been terrible until then).
Yui Hongo (a Priestess in her own right) and Mariko Kobayashi (the protagonist of the Kagami no Miko game, a normal girl accidentally spirited into Hokkan) were in serious risk of being forced into becoming either a Priestess for another God other than the one she summons (Yui) or into a Priestess for a potential new one (Mariko).
Last but not least, Madoka Ootori and Misaki Himuro are the Priestesses of Suzuku and Seiryuu respectively in the video game Suzaku Ibun, where they replace (but also strongly resemble) Miaka and Yui.
- Mariko Kobayashi - potential Priestess for a new God (Kouryuu aka the Yellow Dragon) in Kagami no Miko.
These are the known special abilities displayed by the priestesses throughout their adventures:
- Communication with those outside of the book: While this ability is not exclusive to the priestess in dire situations, it is mainly the priestess who is able to hear whatever is going on outside of the book. As long as she and the reader of the book share a sort of item, she can hear whatever it is the reader is saying.
- Color Glow/ Light: The priestess has the ability to give off a kind of glow during times of danger or great stress. This glow not only confirms that she is the priestess but also allows her to travel out of the book if she has not remained inside of it for too long. And their light also based from what beast god they are summoning.
- Red Light - Priestess of Suzaku (Suzaku no Miko)
- Blue Light - Priestess of Seiryuu (Seiryuu no Miko)
- Silver Light (manga) - Priestess of Genbu (Genbu no Miko)
- Green Light (FY OVA 1 & FY OVA 2 intro) - Priestess of Genbu (Genbu no Miko)
- ? Light - Priestess of Byakko (Byakko no Miko)
- Summoning the Gods: The Beast Gods (Suzaku, Seiryuu, Genbu, Byakko) have bestowed the gift of being able to summon one of them onto the priestesses. Once the summoning ceremony is complete, the priestess is able to grant three wishes.