Matsya Purana — Lineage of Yayāti through Yadu and the Deeds of Kārtavīrya Arjuna
एष नागं मनुष्येषु माहिष्मत्यां महाद्युतिः कर्कोटकसुतं जित्वा पुर्यां तत्र न्यवेशयत् //
eṣa nāgaṃ manuṣyeṣu māhiṣmatyāṃ mahādyutiḥ karkoṭakasutaṃ jitvā puryāṃ tatra nyaveśayat //
This greatly radiant king among men, having conquered the Nāga—Karkoṭaka’s son—at Māhiṣmatī, settled there in that city and established his rule.
This verse is not about Pralaya; it belongs to a royal-legend/genealogical narrative describing conquest and settlement at Māhiṣmatī.
It highlights a kingly duty central to Purāṇic rājadharma: establishing order and sovereignty by defeating hostile powers and then stabilizing governance by ‘settling/establishing’ a secure seat in a city.
No explicit Vāstu or ritual rule is stated; the key takeaway is the political act of founding/establishing a city-seat (nyaveśayat), which later Vāstu-oriented sections often treat as a prerequisite for orderly urban life.