One of our argent scouts, Hailen, is assigned to the outskirts and highlands. She tends to come back to camp every fortnight. Judging by your description, it's possible it was her remains you found. But we haven't seen any other skyborne like you saw at the river bank. We have another field camp, northwest of Blackwood Lake. The medic there may know something about this as well. Quite a bit more to see on the front lines.