Narasimhapurana 36.7

36.7

rāmeṇa bhūtvā ca yathā viṣṇunā rāvaṇo hataḥ
sagaṇāś cādbhutā rājan rākṣasā devakaṇṭakāḥ //

and how, having become Rāma, Rāvaṇa was slain by Viṣṇu, / together with his marvelous hosts, O king, the rākṣasas who were thorns to the gods;