Historians and clerics Manuel Risco and Carlos González de Posada both date his episcopate to 976–92.
Bermudo signs immediately after Ramiro III of León and his regent, Elvira Ramírez.
[3] The likely explanation is that Bermudo, being perhaps old and physically weak, retired formally to a monastery and entrusted daily episcopal duties to an auxiliary bishop, Gudesteus, who would succeed him in full later.
This practice was not uncommon at the time and Oviedo had known an auxiliary bishop earlier in the tenth century (Hermenegild II, fl.
[4] This may be related to the enmity which Bishop Pelagius reported over a century later between Gudesteus and King Bermudo II, who was opposed more generally by the Asturians and Leonese and was consequently forced to seek his coronation in Galicia.