Ersetu
Overview
Miles below Ithara lies the underworld, Ersetu, choked in aether and filled with myriad horrors. This continent-spanning chasm of dim, shimmering light is separated from the surface only by a ceiling of stone and sand that seems to act as a cap on the incredibly dense aether below. Indeed, some scholars have suggested that the source of aether is, in fact, somewhere within Ersetu, and it leaks up from the underworld into Ithara in relatively smaller concentrations.
As fallen kingdoms sink beneath the sands, many of the oldest fall through the porous ceiling of Ersetu, crashing down in mounds of rubble and ruin and corpses. Unparalleled riches through history could be found in Ersetu, but rumors abound that any riches that touch Ersetu’s foul air are immediately cursed.
Entering Ersetu unprotected is almost inevitably a life-changing event. The highly-concentrated aether warps anything that enters, living or dead, into a twisted fiend and bends their minds into a frenzy that knows nothing but terror and fury. These fiends, referred to as gallu in ancient texts or rakshasa in contemporary discourse, terrorize the surface when they manage to claw their way out of Ersetu or are intentionally summoned. At the same time, some holy entities such as the ammit live to hunt these fiends and reside in Ersetu themselves, though as a result they are no less ferocious and bloodthirsty.
Fortunately, save for those few places that touch Ersetu’s sand-sky, Ithara is mostly safe from the underworld below. As a consequence, not many details are known about Ersetu, and most Itharans are content to keep it that way.
