Baator - Avernus

- First layer of the Nine Hells - an endless battlefield between Devils (baatezu) and Demons (tanar'ri) in the Blood War

- Strongly evil- and lawful-aligned

- In the spots where there isn't lava, the blackened, basalt surface is rocky, jagged, and razor-sharp, making travel slow and dangerous 

- The blood-red sky is streaked with smoking fireballs that shoot from pits and volcanic calderas, striking land dwellers seemingly at random (but with a preference for the pure of heart)

- The ruins of countless gate towns stolen from the outlands reside here, as well as even older structures - the remains of an infernal construction project from long ago, before the war came to Avernus

- Gore-soaked rivers of blood streak across the layer, their bottoms thick with bones and giant fiendish leeches... the bloody streams eventually merge with the  Styx, a black, oily scar of a river that can be used as an escape from hell (and to places even worse), but be warned: the Styx's poison waters steal the memories and identities of mortals

– In addition to devil legions and demon hordes, there are innumerable other horrors in Baator, including Hellfire Engines, Hook Spiders, Maelephants, Bonespears, Hell Hounds, Rakshasas, Fhorges, fiend Larvae, Night Hags, Bezekira, and the dreaded Hellfire Wyrm.