As to what happened to Alsea and the two House Elves when they weren’t chosen; Alsea by sheer chance had become pregnant within the small time period with Tom, the Imperial Family had her stay in a room within the Nest to stay until the baby was born, whereas Voski and Meely ended up being assigned to "play" with the colts of Bane’s Herd. By "play" they were tied down with their legs positioned so is to make it easier for the young hormonal centaurs to to gain practice in mounting the fillies, and bend in a way to fuck a non-centaur female.