Oktavia von Seckendorff is a witch character from the anime series 'Mahou Shoujo Madoka Magica.' She is the witch form of Sayaka Miki, one of the main magical girls, after Sayaka succumbs to despair. Oktavia is known for her knightly appearance and her association with music and water motifs, reflecting Sayaka's love and heartbreak. In the series, Oktavia serves as a tragic antagonist, symbolizing the consequences of hopelessness and the darker aspects of being a magical girl.