Complex sentence: All surviving accounts were written by enemies of the Huns, and none describe the Huns as attractive either morally or in appearance (the Huns were illiterate and thus kept no records).
Split into simpler sentences: All surviving accounts were written by enemies of the Huns. Thus, none of these accounts describe the Huns as attractive either morally or in appearance (the Huns were illiterate and thus kept no records).