The Nine Hells

It is the epitome of premeditated cruelty. The devils of the Nine Hells are bound to obey the laws of their superiors, but they rebel within their individual castes. All petitioners endlessly suffer at the hand of the devils. Wild magic is disabled in this realm.

At the end of each long rest taken on this plane, a visitor that isn’t evil must make a DC 10 Wisdom saving throw. On a failed save, the creature’s alignment changes to lawful evil. The change becomes permanent if the creature doesn’t leave the plane within 1d4 days. Otherwise, the creature’s alignment reverts to normal after one day spent on a plane other than the Nine Hells. Casting the dispel evil and good spell on the creature also restores its original alignment.