The people of Zarahemla, later called Mulekites in Latter-day Saint tradition though the Book of Mormon itself does not use that name, are described in Omni as descendants of a separate group that left Jerusalem around the same period as Lehi's family but had, by the time of contact, lost their own written records and their original language had drifted. Their unification with Nephi's people under a shared king, Mosiah, is the event that closes the small plates era and opens the record onto a larger political stage, since Zarahemla becomes the Nephites' capital city for most of the remainder of the Book of Mormon's narrative.
Amaleki's account of this discovery, and his closing appeal to his readers to come to Christ, is the last material composed for the small plates themselves. With no descendant to continue the record, Amaleki delivers the plates to King Benjamin, and the book of Mosiah that follows shifts from small plates authorship to Mormon's later abridgment of the larger Nephite record.
Latter-day Saint tradition later identified the people of Zarahemla as descendants of Mulek, a supposed son of the biblical king Zedekiah, though the Book of Mormon text itself never states this connection directly in Omni; the identification is drawn from a single later remark in the book of Mosiah and has become part of the standard framework used to discuss Book of Mormon peoples.