'messengers', or μαγιστριανοί, magistrianoí, 'magister's men'[1]) were the late Roman imperial and Byzantine courier service and general agents of the central government from the 4th to the 7th centuries.
[2] The schola of the agentes in rebus of the Western Empire did not cease to exist when the West fell, but the office underwent a transformation over the following decades.
Evidence suggests responsibilities differed between the two types of agents, though they likely frequently collaborated with one another due to overlapping interests of the two groups of citizens.
Saiones, who were a part of the Gothic court, were responsible for affairs concerning the king's own people, the Goths, such as serving as protectors for officials, arresting criminals, recruitment for the army and navy, and overseeing the construction of forts.
[7] As for their function, the 6th-century historian Procopius notes in his Secret History: The earlier Emperors, in order to gain the most speedy information concerning the movements of the enemy in each territory, seditions or unforeseen accidents in individual towns, and the actions of the governors and other officials in all parts of the Empire, and also in order that those who conveyed the yearly tribute might do so without danger or delay, had established a rapid service of public couriers.
[1] This role, as well as their extraordinary power, made them feared: the 4th-century philosopher Libanius accused them of gross misconduct, terrorizing and extorting the provincials, "sheep-dogs who had joined the wolf pack".
[12] The numbers of the agentes tended towards inflation,[1] and the corps was viewed with a measure of mistrust by the emperors, who repeatedly tried to regulate its size:[12] 1,174 in the year 430 according to a law of Theodosius II, and 1,248 under Leo I (457–474).