The protective coil timed exactly to darkness: a serpent wraps the luminous, meditating/dead-but-living figure for the whole duration of the dark passage — seven days of storm, twelve hours of night — encircling without constricting, and releases the moment light returns. In both, the coiling serpent is servant and shield, and at the end it withdraws having taken nothing; the Pali text even ends with the serpent's own body abandoned (he 'made his own appearance disappear') as if the coil were only ever an instrument of the watch.
During a seven-day storm 'cold weather, storms, and darkness,' the Naga king Mucalinda 'seven times encircled the body of the Blessed One with his windings' and spread his hood over his head; when he 'saw the open, cloudless sky, he loosened his windings,' took the form of a youth, and stood with clasped hands before the Buddha.
Through the middle hours of the night the sun-god traverses the Tuat standing 'under a canopy formed by the serpent Mehen' — the Enveloper — whose coil covers the god in his boat hour after hour and is quit only at the eastern exit into dawn.
Mahavagga I.3 verified verbatim at SBE 13 pp. 80-81; Mehen canopy formula verified in Budge's Tenth Division text ('under a canopy formed by the serpent Mehen') with the enveloping role running from the Seventh Division onward.
Our fact-checkers corrected the first draft:
The serpent as impounder of water: in both, the serpent takes the waters into its own keeping (encompassed under Vritra's bulk / swallowed into the Bakhu serpent's body), the world's motion stalls (the rivers penned like cattle / the solar barque standing still), and an armed god compels restitution · the waters are given back in full and flow resumes.
Same skeleton with no shared geography: humanity's crime is an affront to the senior god's comfort or dignity, a council formalizes extermination, the killing is halted mid-course by subversion within the pantheon itself, a remnant survives, and the wearied god afterward binds or removes himself.
Both traditions insist the treasures of the first age were not composed by anyone living but FOUND · golden game-pieces standing in the grass, god-written slabs buried in temple foundations · physical leavings of an elder age recovered by later hands.
Two unconnected traditions furnish the between-worlds interval identically: everything drowned back into one primeval water; a span measured in cosmic units (millions of years / a night of Brahma); and the sole survivor a god withdrawn into or onto a SERPENT, explicitly unseen by men and gods, waiting out the gap.