Theophanu was a Byzantine noblewoman, whose uncle acceded to the throne. That she was not herself of imperial descent, not born to the purple (porphyrogenita), but a niece of the man who had taken over the throne in a coup (John Tzimiskes), was a source of disappointment to some when she married the son of Otto I. But Theophanu had been educated to play a role in an imperial court. She was personally impressive and intelligent and she participated in her husband’s government, traveling with him — the court had no fixed center — even on military campaigns.(1) They had five children, of whom four survived: Otto III, Adelaide (abbess of Quedlinburg), Sophia (abbess of Gandersheim), and Matilda (who married the count palatine Ezzo).
When Otto II died in December 983, Theophanu served as regent for their son, Otto III, at first sharing the regency with her mother-in-law, empress Adelaide, but eventually taking over on her own. Through the regency, she was formally associated with her son in his documents and actions, and foreign rulers negotiated with her. She is called imperatrix or imperator in official documents. Though she had differences with her mother-in-law, empress Adelaide, some of them inherited from her husband,(2) the two worked together to secure the throne for Otto III from his cousin, Henry II of Bavaria (“the Wrangler”), who had proclaimed himself king. Theophanu died in 991, still in her 30’s.
(1) Theophanu intervened 76 times during the lifetime of her husband, often making grants that she initiated, according to Karl Leyser, Communications and Power in Medieval Europe, The Carolingian and Ottonian Centuries, ed. Timothy Reuter, (London: Hambledon, 1994), 159. She was nearby, holding the royal treasure, when Otto was defeated in southern Italy in 982, according to Pauline Stafford, Queens, Concubines and Dowagers, The King’s Wife in the Early Middle Ages (London: Batsford, 1983), 90, 105.
(2) It is usually said that the differences were over Adelaide’s dower lands, but there were other issues between them. Adelaide had been a supporter of Henry of Bavaria, whose father had helped her to marry Otto I against the manoeuvres of Liudolf, Otto’s son by his first wife, and Henry had serious disagreements with Otto II. Adelaide’s son-in-law, Lothar, king of France, who was married to Emma, her daughter by her first marriage, invaded the western German area. See Odilo Engels “Theophano, the western empress from the East,” The Empress Theophano, ed. Adelbert Davids (Cambridge: Cambridge University Press, 1995). For more on Theophanu, see Kaiserin Theophanu, Prinzessin aus der Fremde — des Westreichs Grosse Kaiserin ed. Gunther Wolf) Cologne: Böhlau, 1991).