William XXIII Avent

William XXIII of the House Avent is the Emperor of the Sollan Empire, the longest-reigning Emperor in Imperial history, formally titled Firstborn Son of Earth, Guardian of the Solar System, King of Avalon, Lord Sovereign of the Kingdom of Windsor-in-Exile, Prince Imperator of the Arms of Orion, Sagittarius, Perseus, and Centaurus, Supreme Lord of the Cities of Forum, Defender of the Children of Men, and Servant of the Servants of Earth. A scion of the House of Windsor who traces his lineage to Arthur himself, he is also credited as the creator of the Excubitors, the founder of HAPSIS, and the architect of a covert strategy that played his enemies -- the Chantry, the Extrasolarians, and the Cielcin -- against one another throughout his millennium-long reign.

He knighted Hadrian and dispatched him to Gododdin, crowned him with the Grass Crown at the Imperial Triumph on Forum, and privately revealed the mission had been designed to fail. On Nessus he dispatched Hadrian as apostol to the Lothrian Commonwealth rather than yield to Chantry pressure to execute him. He later disclosed secrets about the Acts of Will, the God Emperor's lineage, and HAPSIS, and revealed his intention to find and kill a living Watcher alongside Hadrian. During the Cielcin assault on Perfugium he refused to evacuate, personally tended wounded, and threw Hadrian his own highmatter sword. He formally appointed Hadrian as Auctor of the Imperium from his creche aboard Aurora, granting him full Imperial power and confessing that Dorayaica's attack on Danu was orchestrated as a trap with his blessing. Revived from stasis, he confronted the Chantry at the Imperial court, forced Grand Prior Tarquin to kiss his plague-infected ring, and had the Chantry clergy arrested. He led the party through the Cynon bunker network holding every palatine genome and the means to cleanse them, announced his daughter Selene would rule as Empress after him, and personally performed Hadrian's wedding ceremony, charging him with finishing what they had begun.

William suffers from a lethovirus manufactured by Extrasolarians, causing malignant tumors and uncontrolled tissue growth. By the end, his left arm has been surgically removed, his face scabbed and swollen with unceasing growth, and he lies in a hermetic enclosure in the royal apartments of Aurora. He declares he had meant to see the defeat of the Cielcin, the Chantry, and the Lothrian Commonwealth himself and leave peace to his children, but that he has failed despite more than a thousand years of trying. He formally abdicates by granting Hadrian his eight rings of yellow gold and, having already coded the genetic database to Hadrian's identity, names him his son by adoption and successor, then bows his head to Hadrian in farewell.