Garudapurana 3.28.2

3.28.2

sā pārvatā rudrapatnī khagendra yā śeṣapatnī vāruṇī nāma pūrvā /
saivāgatā balabhadreṇa rantuṃ dvirūpamāsthāya mahāpativratā //

She is Pārvatī, the wife of Rudra, O King of Birds; she who formerly was the wife of Śeṣa named Vāruṇī, / that very woman of great marital fidelity, assuming a double form, came to take delight with Balabhadra.