Dungeon

"Dungeons. That's what we Terrans call them at least. They form in weird places with lots of magic, and often contain valuable things within them." 
-Aaron 
Dungeons are a special type of lesser rift, commonly found throughout Arkon, and following The Convergence, on Earth as well. They occur when a location is flooded with large amounts of magic for long periods of time, causing unique ecosystems to develop as the local wildlife is twisted, and supernatural entities begin to move in. The most famous of these is Le-Mont-Saint-Michel, in France. 
Dungeons form most commonly around the towers of powerful mages, in crypts and ruins that were sites of upheaval or powerful sealing spells, or within other rifts, such as the Faeweald. Many gods and aeons have the power to sense these dungeons, and will place artifacts at their ends for people to discover. 
It is possible to dispel a dungeon, much like one can a rift. Some, called treasure dungeons, collapse after the relic within is claimed. These are often made specifically by a god for the purpose of challenging a potential claimant to the artifact. Others, called fountain dungeons, clear when the magi-ecological balance is disturbed too greatly, causing the ecosystem to collapse. These dungeons are home to monsters of all types, and unless one is particularly harmful to the surrounding environment, the dispellment of a fountain dungeon is considered illegal by the Order of the White Cross, and subject to a hefty fine.