There's a critter in the Antero comic that looks a lot like a Skrael, although I think the impression from that panel in the comic was meant to imply that all the represented races were "old" ones that came into conflict with the Trow and were beaten to a bloody pulp.
Gothmog - Skrael pop up a few times, have a look around for them, but they're basically a light-aligned race that look something like a naga (snakelike, having a snakish head, scaled arms, and a tail instead of legs). Yer-Ks doesn't sound particularly Skrael-ish to me, but since we know so little about them it's bound to be open to interpretation. The fact that the "kingdom" is outlined on the map suggests to me that its boundaries are, and were, well established before its sinking. If Yer-Ks is simply an underwater kingdom, why would it be the only territory to have its boundaries clearly defined on the map?
Personally I think the Northern regions of the Province are fairly conplex and well-populated, and suggest at least five distinct groups inhabiting them; the Skrael, the Provincial settlers, the zerks, whoever the Yer-Ks are, and the fir'bolg, not to mention any seafaring races, Leixian pirates, Bre'unor, etc. With so many conflicting peoples, it seems easy to presume that conflicts would lead to such a cataclysmic event as the sinking of Yer-Ks, much the same as the Callieach/Trow conflict.
