Contrasting the character traits and the behaviour of a good ruler and a tyrant is one of the traditional motives of Byzantine literature. Essential constituents of this comparison were four cardinal virtues (temperance, prudence, justice, and fortitude), philanthropy, piousness, accession to the throne, concern for subjects, and choice of confidants. Each writer did not necessarily discuss all the elements mentioned; he simply chose those that corresponded to his intention and his conception of his literary work. The same writing strategy was used by Nikephoros Bryennios, a Byzantine military commander and historiographer of the 12th century, in his work titled Hyle historias, in which he depicted in detail the reigns of three emperors: Romanos IV Diogenes, Michael VII Doukas, and Nikephoros III Botaneiates. Bryennios ascribed to each of them some typical traits of a tyrant; Romanos lacked prudence, Michael fortitude, and Botaneiates temperance. Furthermore Romanos listened to flatterers, Michael was manipulated by the eunuch Nikephoritzes, and Botaneiates consulted the dishonest barbarian Boril and trusted the perfidious eunuch John. The examples given imply that, from the list of characteristic mentioned above, Bryennios focused on the choice of confidants and used depictions of the emperor’s confidants to complete the portrayal of the emperor himself. The aim of this paper is to analyze the application of this technique in Hyle historias, which created negative portrayals of former emperors and paved the way for the future emperor Alexios Komnenos, the true hero of Bryennios’ writing.