Years later — the mothers dead, the brothers' sons established in kingdoms — Time (Kāla) comes as an ascetic with a message for Rāma alone: their conference must be private on pain of death to any intruder; Lakṣmaṇa is set at the door. The message: Brahmā recalls Viṣṇu — the descent's term is complete. As if on cue, the irascible Durvāsas arrives demanding immediate audience, threatening to curse the whole lineage; Lakṣmaṇa, weighing his own life against the dynasty, walks in. The word must be kept: Rāma must "abandon" him — and on Vasiṣṭha's counsel, abandonment (for the righteous, exile equals death) is pronounced instead of execution. Lakṣmaṇa goes to the Sarayū, suspends his breath in yoga, and is taken up bodily by Indra — the first departure, and the epic's last keeping of a terrible word: the brother who joined the exile unasked leaves first, by the door of the very satya he served.
Mahāprasthāna
Rāma divides the empire — Kuśa and Lava enthroned in Kosala's halves; Bharata's and Śatrughna's sons established — and walks out of Ayodhyā for the last time, Vibhīṣaṇa charged to remain Laṅkā's king while the sun endures, Hanumān blessed to live as long as the Rāma-story is told (the boon under every Rāmāyaṇa recitation since), and Jāmbavān till the next yuga's need. Behind him come the brothers, the court, the citizens down to the animals — an entire civilization declining to survive its king. At the Sarayū, Brahmā's voice from heaven: "Enter, Viṣṇu, with your brothers — your forms of glory await." Rāma walks into the water and resumes Viṣṇu-hood; the people who followed rise with him. The epic that began with grief become verse ends with a world unable to remain behind its Rāma — and with the poem itself, in Vālmīki's last frame, left as what remains of him on earth.
Kamba Rāmāyaṇam differs
None of the Uttara exists in Kambar's hand — his Irāmāvatāram has already ended in coronation joy (the Tamil Uttara Kāṇḍam being attributed to Oṭṭakkūttar). The comparative lesson is the two epics' final theologies: Vālmīki's frame treats dharma as tragic — its perfect servant loses everything to it, twice — while Kambar's treats the descent as saving līlā, properly ending where salvation completes. Which ending one holds determines which Rāmāyaṇa one has read; a full study should hold both.