| Category | Caverns |
| Continent | Brucrumus |
| Region | Adunamar |
| Alias | Descend One |
| Map | Vul Sahsir |
Tumbo Gein is a passage that links Vul Sahsir with its surface counterpart Krein Jusk. On the surface, this passage ends at half-submerged caves along the western shores of lake Lokzii Ahraan. In the Lith-Crillion Era, kuo-toans followed the Sea Tunnel to Rath Vun. In this area, they were sucked upward to the mixing waters of lake Lokzii Ahraan. Unaccustomed to the bright skies, they sought refuge in these caves; eventually finding a passage descending deeper into the darkness. This passage, the Tumbo Gein, descends into the region Adunamar. The kuo-toans left this passage, entering a massive cavern called Vul Sahsir where they founded the settlement Zoethall. The kuo-toans frequent this passage, raiding the surface for sacrifices to their dark god.