Matsya Purana — Narasimha’s Victory over Hiraṇyakaśipu and the Catalogue of Apocalyptic Omens
असुराणां विनाशाय सुराणां विजयाय च दृश्यन्ते विविधोत्पाता घोरा घोरनिदर्शनाः //
asurāṇāṃ vināśāya surāṇāṃ vijayāya ca dṛśyante vividhotpātā ghorā ghoranidarśanāḥ //
For the destruction of the Asuras and for the victory of the Devas, many kinds of dreadful portents are seen—terrifying signs that foretell a terrible outcome.
It does not describe Pralaya directly; it frames “utpātas” (portents) as cosmic indicators that a major overturning of power is imminent—here, the fall of Asuric forces and the rise of the Devas.
In Purāṇic ethics, recognizing ominous signs is tied to prudent action—kings are expected to consult learned counsel and perform protective rites, while householders respond with restraint, charity, and dharmic conduct rather than panic.
No Vāstu rule is stated, but the verse belongs to the omen-framework often used to justify śānti/propitiatory rites (pacifying rituals) undertaken when alarming signs appear.