Chief Prior who speaks the word of the Ori. He resides in the city of Celestis, his chambers adjacent to the Flames of Enlightenment. The Doci is arguably the most devout believer in Origin, and was the leader of the Ori's human representatives before the birth of the Orici.
The Doci often serves as a direct mouthpiece for the Ori, who literally speak through him. When this happens his eyes will glow red. After his encounter with Dr. Jackson the Ori spoke through the Doci, giving the order for more Priors and the construction of ships to spread Origin to every corner of creation.
The Doci was eventually exposed to the light of the Ark of Truth, realizing the error of his ways after he learned what his "gods" truly were.
Origin - The Doci confronts Dr. Jackson regarding the teachings of the Ori.
The Fourth Horseman, Part 1 - The Doci is on hand to convert the Jaffa leader Gerak into a Prior, by means of the long-distance abilities of the Prior staff.
Stargate: The Ark of Truth - The Doci is exposed to the Ark of Truth, transmitting the truth about the Ori to his Priors across two galaxies.