The Nine Hells

The Nine Hells of Baator inflame the imaginations of travelers, the greed of treasure seekers, and the battle fury of all moral creatures. It is the ultimate plane of law and evil and 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. Most undertake any plot, no matter how foul, to advance themselves. At the very top of the hierarchy is Asmodeus, who has yet to be bested. If he were to be vanquished, the victor would rule the plane in turn. Such is the law of the Nine Hells.
Optional Rule: Pervasive Evil Evil pervades the Nine Hells, and visitors to this plane feel its influence. 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.

Lower Plane
Alignment:
LE

Planar Backdoor to The Scaled Tyrant 's domain

Planar backdoor to The Lord of the Nine Hells 's domain

Source of The River of Fire, Phlegathon