From the introduction:
The party is trapped in an unknown level of a super-dungeon. They entered it, hoping to find fortune and fame, but got lost. Now, many years later, the characters have almost turned into monsters themselves as they continue to explore the dungeon. They live on what they can scavenge or create with magical spells. They have adapted, but they suffer. The memories of life before they ventured into the dungeon are painful, and every day is a fight for survival.
The repeating pattern of fight, loot, go left, go right, fight, loot, move on, fight, rest – has turned the characters insane, so they are now living out the extreme version of their personalities.