Underworld
A very very dark place..
Each Continent, Seridia and Irillion, has it's own UW.
The Underworlder Perk allows players to escape the UW with magic or a teleport ring.
Under normal circumstances you will have to walk out of the UW to travel to over places again.
Another way of going to the UW without dying is with the Hellspawn Perk.
Mines are often placed at the UW exit for players that have the One Perk so that they will drop items, when they are in their weakest condition.