Beneath the surface region Troll Bogs lies its underside, a low-light realm often considered just as damp and marshy as the land above it. This Underdark region is called Slilp-Urp. It receives an abundant amount of groundwater seepage from the wetlands above, causing it to resemble an underground rainstorm in certain areas. However, only a small fraction of this water reaches the Pearl Sea, as the rest drains into deeper tiers. This design is intentional, as Slilp-Urp features a lattice of porous rock that serves as a drainage system, channeling the water even deeper. These specialized rock seams were meticulously created for this region. The Prime Architect collaborated with Silvanus to establish a system capable of draining the excess water emanating from the Radullu Rift. This assistance from the Prime Architect would ultimately prove to be his undoing.
In the Horgon Era, the city-state Nagdúrzol utilized their alien technology to blast away the ancient lava tubes of the Orngrek to the river Sadregnen. These were subsequently flooded, granting Nagdúrzol access to the Pearl Sea. One of the most convenient routes to reach this Slilp-Urp is through the Tûnin-Gil sea caves. At present, these caves, widened and expanded by the Nagdúrzol, allow sailing vessels to depart the open skies and enter the shadowed realms of Slilp-Urp.
