pāpaḥ parama-dāruṇaḥ

yena-by whom; avrtah-covered; ime-all these; lokah-planets; tapasa-by the austerity; tvastra-murtina-in the form of the son of Tvasta; sah-he; vai-indeed; vrtrah-Vrtra; iti-thus; proktah-called; papah-personified sin; parama-darunah-very fearful.