Against R'yleh LAm Atlantis might need to watch out more for shambler thralls than illthids. Illithids cost 2x that of arssartut (and 4x the maintenance) while shambler thralls cost the same 25 gold. Instead of fielding 50 illithids he can field 100 shambers or a combination, which could be quite effective (of course this assumes that R'yleh has a 2:1 advantage in gold income).
