Redguards, Hammerfell and Yokuda.
I have read the lore on Atmora the other day and thought I should wrote a blog on this theory. Little is known of the mysterious continent. Nothing in the previous games actually states what was the catalysm that sunk the continent, just that "something" happened. What have happened to the Yokudans who were never made it to Hammerfell? they could have become a long-lost tribe of the Redguards and went native similiar to the Skaal.
The Redguards from Yokuda does not simply drop their anchor in Hammerfell harbours, rather many of the settlers landed on Herne (PGE1). The vanguard Ra'Gada continued on and arrived in Hammerfell in 808. They slaughtered or enslaved the beast-folk, Nedic peoples, and Orcs of the region in a quick albeit bloody war…