The Gauntlet Arcane

From the introduction:

No clues remain to the original purpose of this level of Dragon’s Delve. Its function and design were completely discarded by the Mages Four during the height of their power and influence over the dungeon. It was during this time that they were constantly engaged in the creation of new magical items, the breeding of unique creatures, and the development of new spells. Like any good scholars, they felt the need to test the efficacy of their creations in a controlled environment before releasing them into the broader world. To facilitate and monitor that process, they built the Gauntlet Arcane.