Hellgate

An ancient underground beneath the elven city of Ab'Dendriel, full of secrets and dangers. Used as a place where convicts are sent.
The door to the entrance is locked and can only be opened with a certain key which can be purchased from Elathriel for the right amount.

You can see many interesting things there, including bridges over hot lava, mysterious treasures hidden behind stones, and a Bonelord library.
It's worth stocking up on food, as it's hard to get it in the center of Hellgate.
Alternatively, you can go back and forth, looking for food in Rotworms or head to Draconia in search of Dragon Ham in Dragons.

It is through Hellgate that one must pass to get to the island of Draconia to perform the Draconia Quest, Dragonfetish Quest, for example.

Recommended: levitate spell or 6 parcels.

Hellgate Entrance

Exiting Hellgate
The entrance itself is not much trouble, the bigger problem is with the exit. Below is a map showing the escape route:

After taking the path marked 9, use the spell levitate or 6 Parcels to enter the teleport. The path ends in a cave full of wasps near Ab'Dendriel.

Creatures: Rat, Spider, Bug, Rotworm, Carrion Worm, Skeleton, Elf, Elf Scout, Ghoul, Gazer, Slime, Bonelord, Crypt Shambler, Elder Bonelord, Giant Spider.