Forgotten Swamp
From Grimhaven Wiki
Forgotten Swamp is a custom map. Located north east of the town Rissne.
You can access it by entering Thais depot and go down a floor there you will find a teleport.
The Forgotten Swamp is also home to the Deep Hive Quest.
Creatures that can be found here:
Snake, Swamp Troll, Swampling, Minotaur, Minotaur Guard, Minotaur Archer, Minotaur Mage, Minotaur Amazon, Minotaur Hunter, Poison Spider, Tarantula, Giant Spider, Necromancer, Priestess, Earth Elemental, Earth Overlord, Spidris, Spidris Elite, Frazzlemaw, Guzzlemaw, Hideous Fungus, Hive Overseer, Defiler and Plaguesmith.
For more information about where check out Spawns.