Procopius

One of the chief sources of the Gothic Wars and of 6th century Byzantine history is Procopius of Caesarea (c.500 - c.565), a Greek scholar and historian from Palestine. Besides writing Words on the Wars, he also wrote something now called Secret History because it contained anecdotes dotes that would be dangerous to him if published in the lifetime of his subjects, and On Buildings, a book about Emperor Justinian's public works.

Justinian came to the throne in 527, and in that same year Preocopius became the legal advisor to Justinian's chief military commander, Belisarius. Procopius followed Belisarius through his various campaigns, both losses and victories, in places as varied as the banks of the Euphrates, Constantinople (where Belisarius suppressed riots with mass executions in the Hippodrome), the Vandal Kingdom in North Africa, and the wars in Italy to re-unite the Western Roman Empire with the Eastern.

Historian Edward Gibbon claimed that Procopius "successively composed the  history, the panegyric, and the satire of his own times." He both admired and criticized Belisarius and Justinian.

Procopius also gives us a firt=st-hand account of the Plague of Justinian, living through its first appearance and more:

During these times there was a pestilence by which the whole human race came near to being annihilated. Now in the case of all other scourges sent from heaven some explanation of a cause might be given by daring men, such as the many theories propounded by those who are clever in these matters; for they love to conjure up causes which are absolutely incomprehensible to man, and to fabricate outlandish theories of natural philosophy knowing well that they are saying nothing sound but considering it sufficient for them, if they completely deceive by their argument some of those whom they meet and persuade them to their view. But for this calamity it is quite impossible either to express in words or to conceive in thought any explanation, except indeed to refer it to God. For it did not come in a part of the world nor upon certain men, nor did it confine itself to any season of the year, so that from such circumstances it might be possible to find subtle explanations of a cause, but it embraced the entire world, and blighted the lives of all men, though differing from one another in the most marked degree, respecting neither sex nor age.

He offers us details that seem unlikely:

Apparitions of supernatural beings in human guise of every description were seen by many persons, and those who encountered them thought that they were struck by the man they had met in this or that part of the body, as it havened, and immediately upon seeing this apparition they were seized also by the disease. Now at first those who met these creatures tried to turn them aside by uttering the holiest of names and exorcising them in other ways as well as each one could, but they accomplished absolutely nothing, for even in the sanctuaries where the most of them fled for refuge they were dying constantly.

Tomorrow we'll look at his description of the symptoms.