Dungeons are open-world areas where specific monsters gather. Most dungeons have a theme or content that ties together not only the monsters that are present but also the dungeon's location within Midgard. The Glastheim dungeons, for example, feature undead monsters in the Glastheim location and there are rumors that the monsters are the former citizens of the city. Many dungeons require adventurers to complete an access quest in order to enter them and there are many quests that involve sending players to various dungeons to hunt monsters or to collect items from them.
Recently, there have been even more difficult dungeons emerging. Adventurers have reported going to places like the Clock Tower and finding themselves facing incredibly difficult monsters unlike anything they had seen. The horrors these adventurers have faced have led many people to call these new, challenging dungeons "Nightmares."