Complex sentence: Just as he lifted his axe to severe Shankara's head, Lord Vishnu as Narasimha entered the body of Shankaracharya's disciple, Padmapada, who was a devotee of Narasimha, and fought the Kapalika, slayed him and thus freed the forest of Kapalikas.
Split into simpler sentences: Just as he lifted his axe to severe the head of Shankara, Lord Vishnu as Narasimha entered the body of the disciple of Shankaracharya and Narasimha devotee, Padmapada. He then fought the Kapalika, slayed him and freed the forest of Kapalikas.