Short answers, pulled from the story.
The Codex Hermogenianus is a collection of imperial legal pronouncements, mostly rescripts to private petitioners, issued by the emperors of the first tetrarchy between 293 and 294. It was compiled by the Roman jurist Aurelius Hermogenianus, who served as magister libellorum under Diocletian. Most of the original work is now lost.
Aurelius Hermogenianus compiled the Codex. He was a prominent jurist who served as magister libellorum, the official drafter of responses to imperial petitions, at the court of Diocletian. The fifth-century author Coelius Sedulius attributed three editions of the work to him.
The core of the Codex was compiled from rescripts dating to 293 and 294, texts Hermogenianus had himself authored in his role at the imperial court. A second edition is thought to have followed after 298, and a possible third edition is dated to around 320.
On the 26th of March 429, Theodosius II directed the creation of what became the Codex Theodosianus, citing the Gregorian and Hermogenian Codes as the model for organising imperial constitutions since Constantine I. The directive was addressed to the senate of Constantinople and drafted by the quaestor Antiochus Chuzon.
Two sixth-century codification projects replaced it: the Breviary of Alaric, promulgated in 506, explicitly superseded the original throughout Visigothic Gaul and Spain, while Justinian's Codex Justinianeus, in force from 529, absorbed its texts and replaced it across the eastern empire and, after conquests, in north Africa and Italy.
Through its incorporation into the Corpus Juris Civilis under Justinian, the Codex Hermogenianus fed into the revived Roman law tradition of the medieval and early modern periods. That tradition was the model for the civil law codes that have shaped European legal systems since the Code Napoleon of 1804.