I was reading about the howling madness of Pandemonium in my old Planescape box set. It's an infinite network of tunnels. Through it whips a screaming, insanity-inducing wind. It's always dark. Desperate lunatics scramble through the madness, slaughtering at will and violating one another in unspeakable ways.
It's not unlike real life. Like Gaza, Ukraine or Iraq.
Below is a filthy, deranged resident of Pandemonium. His horns and tail speak of an Infernal bloodline. With tieflings, you never know.
Denizen of Pandemonium: Armor Class 9, Hit Dice 1. Hit Points 5, No. of Attacks 1, Damage 1d6+1 (spear), Save as Fighter 1, XP Value 20, Alignment CN(e)
Upon meeting the party or lone PC, the denizen will pursue one of the following courses of action:
1) aggressive fornication
2) incoherent babbling