Gehenna, one of the Lower Planes, is the realm of True Evil, its purest form, undiluted by Law and Chaos. The plane is home to many vile creatures, most notably however, the Chthon.

Gehenna consists of five layers:

1. Khalas: A landscape of red and black rocks and mountains, marred by hellfire and volcanoes flowing from the Nine Hells and the swirling Chaos of the Abyss.

2. Mungoth: A land of falling ash and burning snow.

3. Oinos: A land of disease.

4. Niflheim: A land of dark grey forestlands.

5. Hades: The Grey Waste, a vast flat landscape of greys and blacks, home to creatures of unrivalled evil.