The "Histories" of Agathias, a lawyer from Constantinople, continue the work of Procopius on the last years of the eventful reign of Justinian, covering the period 552-559. It is the most important source for the events it narrates, and for some of them, the only one. It contains a detailed description of the Frankish invasion of Italy in 553, which was ultimately repelled by the brilliant general Narses, the History of the Roman-Persian War in Lazica, the assassination of the Lazic king Goubazes, and the dramatic trial and conviction of the culprits by a Roman court. It concludes with the invasion of the Kutrigur Huns, who reach the outskirts of Constantinople, only to be defeated by the strategic expertise of the retired and elderly general Belisarius.

Equally significant and highly interesting are the digressions on the nature of History, the customs and religious practices of the Persians, the discussions and quarrels of a vulgar group of pseudo-philosophers, the pranks concocted by the inventive imagination of the engineer and architect of the Hagia Sophia, Anthemius, at the expense of his neighbors, and more.

Finally, the author's confession regarding his aversion to the profession of lawyer, which, while providing him with a livelihood, keeps him away from his true love, History, gives a personal tone to the narrative, which is absent from most Byzantine historical texts.