Lucidonius was the founder of the Seven Satrapies, the one who established the Orholamic faith as the state religion, the first emperor of the empire, and the first Prism.
During his tenure as Prism, he established the Blackguard to protect the Prism, the Spectrum, The White, and The Chromeria, but also to serve as a check on the Prism in case he/she started to go mad with power.
Lucidonius was married to Karris Atriel, later known as Karris Shadowblinder, who served as a member of the Blackguard and succeeded Lucidonius as the second Prism after his death.
According to Seven Satrapies teaching, Lucidonius was "an outsider to the Parians." This is alternately interpreted to mean he was a non-Parian, or an outsider among them, being a Parian but being different from all the others. The stained-glass-window depiction of Lucidonius shows him having dark skin like a Parian, but lighter than the skin of the Parian figures surrounding him.
Lucidonius was accompanied/protected by 30 mighty men, some of whom only followed him after he defeated them in combat. Many of them, before joining Lucidonius, had been heroes and priests of the Old Gods, and had names taken from them, such as El-Anat, Dangar Zelan, and Or-Mar-Zel-Atir. When they pledged themselves to Lucidonius and, by extension, Orholam, they took new names. El-Anat eventually became known as Shining Spear. This tradition carried over to the Blackguards, which is why Kip was given a "Blackguard name" during Blackguard training: that of Breaker.