Diggle Hell is a dimension added with Conquest Of The Wizardlands. It can be accessed at any point after acquiring the keys to the Pocket Dimension. Entering anything other than a valid Arcane Address into the Pocket Dimension Portal Generator will result in a portal to Diggle Hell opening instead; it can be distinguished by a red tint instead of the normal black. However, it is extremely ill-advised to go to Diggle Hell until the endgame, as it is full of extremely powerful enemies who can easily kill an underequipped character. If you're really (un)lucky, you may even meet Vlad Digula, who will destroy you. Fun for the whole family, or your zorkmids back!
Much like a proper Wizardland, Diggle Hell features a randomized layout, loot, monsters, and an exit portal. It may be thought of as, essentially, an unlimited, repeatable Wizardland, a way to endlessly farm XP and loot if you've cleared the whole dungeon but aren't quite ready to take on Dredmor. As the level may be randomly generated over and over again for as many times as the player is able to beat it, it is very useful for gaining those last few levels or that last piece of gear to complete your set. However, it is considerably more dangerous than the average Wizardland due to the risk of meeting Digula, so one should be exceptionally cautious when farming Diggle Hell.
Diggle Hell is the only place where the statue of the Diggle Devil may be found. It is also the only place where Vlad Digula can spawn.