A map of the relevant part of Tiasa is included with some of the Kickstarter prizes. And obviously it's included in the book. Here's a quick video of the process of drawing said map.
Music credit goes to the guys and gals who composed the Suikoden Tierkreis soundtrack.
Voice credit goes to the one typing this now (Yay, a riddle!).
In the video I mention that (canonically) Brandal might be who drew this map... But if that were true, there'd be spoilers and a lot more detail. Berdes has no record of any cartographer exploring the Unwithering Woods. Plus, a lot of the details in the map are in an overview type of style... As if drawn by someone up high... maybe even on an island in the sky.
It's settled. The map came from Suvinor. Which is "lofty as a stork's arse," as Vodnik would explain.