Complex sentence: In previous epics Morgan had not been named as sister to arthur, however in Chrétien de Troyes poem "Erec and Enide" Morgan is transformed from sorceress to sister, this innovation was followed by Stephen in the "Draco".
Split into simpler sentences: In previous epics Morgan had not been named as sister to Arthur. Only in in Chrétien de Troyes poem "Erec and Enide" was Morgan transformed from sorceress to sister, and this innovation was followed by Stephen in the "Draco".