Matsya Purana — The Observance of Ananta-Tritiya
पूर्वेण विन्यसेद्गौरीम् अपर्णां च ततः परम् भवानीं दक्षिणे तद्वद् रुद्राणीं च ततः परम् //
pūrveṇa vinyasedgaurīm aparṇāṃ ca tataḥ param bhavānīṃ dakṣiṇe tadvad rudrāṇīṃ ca tataḥ param //
On the eastern side one should install Gaurī, and thereafter Aparṇā; on the southern side likewise one should install Bhavānī, and thereafter Rudrāṇī.
This verse is not about pralaya; it gives a Vastu/ritual directive for arranging specific forms of the Goddess in particular directions within a sacred layout.
For a king commissioning temples or a householder establishing a shrine, the duty is to follow śāstric order in consecration—placing deities by direction to maintain ritual correctness, auspiciousness, and communal religious harmony.
It specifies directional placement in the temple/mandala: Gaurī and Aparṇā to the east, and Bhavānī and Rudrāṇī to the south—an iconographic rule used in planning niches, subsidiary shrines, and installation sequences.