The unnamed horror downstream

I'm continuing to salvage the Shadow Elves' south. To that I have some observations about downstream of Losetrel, in the map. Here follows the original from the PDF.

The elves have set up multiple fortifications here. Sylaros is a "fortress", which I assume is a walled town or village. Twenty miles further in, Durfyn's Belfry is another tower by icon - but I think it's an aerie. Durfyn skinwings shuttle to/from the Dragon Lake over the Lost Souls. In transit these flights are always accompanied by shamans.

The map's also etched out a "secondary" footpath between Sylaros and Losetrel's southern bank. This path serves to bypass the Sojourner, in case anyone wanted to route around the north (through the Lost Souls) or the south. Travelers will consider the southern riverbend: down the Sojourner, up the Gilfyn. It can't be much less navigable than the path. So I question the safety of the river downstream of Losetrel.

The elves could write off the entire Elmglow cavern - indeed, my earlier posts here have argued that the Elmglow was a stray thread, and worked around it. In this salvage-operation, I counter-assume there's something the elves need, in its western spur Vyarii. For that, the Mylandiel cave looms to the west of the Belfry. This offers strategic-depth for the garrison there.

"Mylandiel" mainly applies to the highland. The elves own nothing here directly and specifically. Geographically Mylandiel slopes downward to the northern mudflat - steeply. That is why the middle section is marked as mountain, and why the southern "hills" are dry. These "hills" are indeed a highland, relative to the rest.

The map does propose a mine in the caves south and more southeast of that. I doubt the spiders or the living dead do anything here either.

Whatever's in Mylandiel, it's peril enough to hamper further exploration downstream. The elves have enough of the cavern secured that the east of its highland offers strategic-depth for the Belfry. Maybe they let captives loose here for their skinwings to hunt. Maybe the Mylandiel cave is where the elves put their skinwings out to stud.

If Mylandiel is their skinwing ranch then it is also their southwest border-buffer. Protecting and maintaining that is why the elves need their Vyarii fortifications.