Revākhaṇḍa ascribed to the Vāyupurāṇa (RKV) 17.12

17.12

tato ravijvālasahasramāli babhūva vaktraṃ calajihvadaṃṣṭram /
maheśvarasyādbhutarūpiṇas tadā sa dvādaśātmā prababhūva ekaḥ //

Then the face, possessing moving tongues and fangs, became garlanded with thousands of sun-like flames; / then, of Maheśvara of wondrous form, that single [face] became twelvefold in nature.