Brimstone is a set of free wargames rules for 15mm to 28mm skirmish battles in Hell. Written by Anreas Udby, the premise is that the Prince of arkness has been slain, and that his lieutenants are battling for control of the underworld. It's cleverly written, with lines like this:
Panic. There�s also no such thing as morale in Hell. Face it -- to have morale, you really need to have such a thing as happiness. In Hell, there are really just shades of panic, hopelessness, and utter despair.
Another part I like is that it turns out that Hell has a caste system and the various denizens won't always play nice together.
All in all, an imaginative work.