He had risen to power from abject poverty, and like other such people had remained greedy; his ambition grew with success, like gangrene invading a body
ἀπὸ ἐσχάτης πενίας καὶ τύχης ἀφανοῦς. Anna Komnene 122.55-64
He was extremely ingenious and a deep thinker
μηχανικώτατος ὢν καὶ βαθύνους. Anna Komnene 125.75
Was one of the Franks (Normans) who entered the service of Georgios 62 Maniakes and remained in Italy when the latter rose in rebellion against Monomachos (Konstantinos 9)
Ἦν δέ τις ἐν αὐτοῖς Ῥουμπέρτος τοὔνομα. Skylitzes Continuatus 167.13-16
A terrible and hot-tempered man, he had a tyrannical disposition
He was peace-loving, profoundly Christian, intelligent, noble and legitimate - traits which attracted Michael 7 to propose a marriage alliance
Psellos Letters (Sathas) 143-144.385-392
His power and fame grew as the Roman army was busy with civil wars after the death of Monomachos (Konstantinos 9), the one-year reign of Theodora 1, the accession of Michael 6 and the rebellion against the latter by Komnenos (Isaakios 1)
On the same day (as they say), the Byzantine and German emperors saw his victorious standards and were terrified
cujus signa sub uno, ut aiunt, die Graecus Alemannusque imperator tremuerunt victricia. Ralph of Caen 1
[A substantial encomium.] An excellent leader, intelligent, of fine appearance, an amusing speaker with a quick tongue and loud voice, approachable, of tall stature, with hair well cut ...
[As well as his positive characteristics...] he was miserly, grasping, with a mercenary spirit, a great lover of possessions and above all full of ambition