Basileus

For two centuries its towers and domes were to rise in the heavens, drawing the attention of Emperors and Basilei, of Popes and Patriarchs.

Source: wiktionary

Although portrayals of basileis of the eleventh century wearing the loros in the traditional manner are not lacking, I cannot cite a Byzantine example of metropolitan origin later than 1100.

Source: wiktionary

The revitalization of the Byzantine Empire during the reigns of the energetic and capable basilei of the Comnens dynasty: Alexios I (1081-1118), John II (1118-1143) and Manuel (1143-1180), and the wars with a Rum Sultanate troubled by dynastic fights drastically diminished its possessions in Anatolia.

Source: wiktionary

It is quite easy to establish the identity of these “Roman princes” who reoccupied Pannonia after Attila’s death: they were the basilei from Constantinople who, after the fall of the Western Roman Empire, claimed to be the only successors of the Caesars (around the turn of the 9ᵗʰ century they began to call themselves “basilei of the Romans”—“basileis ton Romanon” or “Romaion”).

Source: wiktionary