In 855, however, Michael III turned fifteen and thus came nominally of age. The young ruler began resenting the dominance of his mother and of Theoktistos, especially after they selected Eudokia Dekapolitissa as his bride, disregarding Michael's attachment to his mistress, Eudokia Ingerina. Supported by his uncles Bardas and Petronas, Emperor Michael had Theoktistos seized and killed in late 855, while Petronas undertook the confinement of the empress and her daughters into a monastery.
In 855, Michael III reached the age of fifteen, thus becoming legally an adult. The young ruler began to resent his mother and Theoktistos, especially after they chose Eudokia Dekapolitissa as his bride, ignoring Michael's affection for his mistress, Eudokia Ingerina. Supported by his uncles Bardas and Petronas, Emperor Michael had Theoktistos seized and killed in late 855, while Petronas confined the empress and her daughters to a monastery.