Matsya Purana — Śrāddha Procedure: Types
कृतघ्नान्नास्तिकांस् तद्वन् म्लेच्छदेशनिवासिनः त्रिशङ्कुर् बर्बरद्राववीतद्रविडकोङ्कणान् //
kṛtaghnānnāstikāṃs tadvan mlecchadeśanivāsinaḥ triśaṅkur barbaradrāvavītadraviḍakoṅkaṇān //
Likewise, he (Triśaṅku) drove away the ungrateful (kṛtaghna) and the unbelievers (nāstika), as well as those dwelling in mleccha lands—including the Barbaras, Drāva-vītas, Draviḍas, and Koṅkaṇas.
Nothing directly—this verse is not about pralaya; it is a Purāṇic catalogue-style statement about peoples/regions and a king (Triśaṅku) expelling groups labeled as nāstika or mleccha-dwellers.
It reflects a Purāṇic ideal of kingship where the ruler is portrayed as protecting Vedic social order—rewarding loyalty and excluding those seen as hostile to dharma (here framed as ‘kṛtaghna’ and ‘nāstika’), though the labels are culture-specific to the text’s worldview.
None is stated in this verse; it is a regional/ethnic listing rather than a Vastu, temple-building, or ritual instruction.