Matsya Purana — The Terror of Tripura and the Gods’ Hymn to Śiva
सिंहनादे व्योमगानां तेषु भीतेषु जन्तुषु त्रैलोक्ये भयसंमूढे तमोन्धन्वम् उपागते //
siṃhanāde vyomagānāṃ teṣu bhīteṣu jantuṣu trailokye bhayasaṃmūḍhe tamondhanvam upāgate //
As the sky-ranging beings roared like lions, all creatures became terrified; the three worlds, bewildered by fear, were overtaken by a blinding mass of darkness.
It portrays classic pre-pralaya portents: unnatural roaring sounds in the heavens, universal panic among beings, and an all-enveloping darkness overtaking the three worlds—signals of cosmic disorder preceding dissolution.
Indirectly, it frames why dharma emphasizes steadiness in crisis: when collective fear and confusion spread, rulers and householders are expected to maintain courage, order, and ritual discipline rather than succumb to panic.
No direct Vāstu or temple-building rule is stated; ritually, the imagery supports the Purāṇic idea that during ominous darkness and fear, protective rites (śānti, japa, homa) are prescribed to restore auspiciousness.