Sarl is a feudal, pre-industrial humanoid race living on the eighth and ninth levels of the shellworld of Sursamen. Shellworlds are ancient artificial planets consisting of fourteen nested concentric spheres internally lit by tiny thermonuclear "stars," whose layers are inhabited by various races. Constructed for an unknown purpose by a long-dead race called the Veil, shellworlds are guarded and mentored by progressively more advanced species, up to the level of what the Sarl call "Optimae." (The Optimae themselves, particularly the Culture, prefer the term "Involved.")
The Oct, the direct mentoring species over the human Sarl, tried to take over the ninth level of Sursamen, using the Sarl royal court and military as their pawns. It became clear that they searched for something hidden in the Nameless City, a metropolis buried under several hundred million years of sediment which is currently being stripped away by the giant Hyeng-zhar waterfalls. The ninth level was only recently re-colonized in a move by the Oct, which was retrospectively validated, with reluctance, by Sursamen's mentoring races, the Nariscene and the more senior Morthanveld.
The Sarl are enemies of the Deldeyn.