I wanna know what kind of a cave is likely to have a demon fort in it. I've got this character, you see, who's been kicking butt for a good while now, and I wanna send him down to hell (since, let's face it, dying while fighting the legions of hell is pretty much the most badass way to die for any character), but to do that, I need to know what kind of a cave I need to seek out. Mountain cave, evil mountains cave, forest cave, cave with a long name and a bunch of megabeasts in it?
A cave is so far removed from hell, it is just the beginning of an extremely long journey.
Any cave that connects to the cavern system will do, once you are in the first level cavern you must search for the way downwards, which will be announced by "you have found a downward passage", although the ways up are also announced in such a fashion.
You must descend twice, no mean task in itself, until you have reached the third level. Navigate the third level until you find a curious structure, these too will be announced.
The underground galleries are composed of many "blocks" (the size of embark squares) of caverns, which are not continuos/overlapping with neighbouring blocks, connecting to these only in a number of entrances and exits, occasionally not at all, forcing you to turn back after you have just spent an hour furiously searching for a way forward.
Beware certain descents that may seem like a way to a deeper cavern (they go down about 20 levels), but that do not announce themselves and lead only to a massive and frustrating maze with few exits, of which all lead to the level you had just "descended" from.
Take care if you are in an area barren of underground trees, certain areas are devoid of creatures and I believe those without trees are more likely to be so, it is entirely possible to starve to death as you scourge the lifeless halls in search of beasts to slay and consume.
Any friends and followers you bring with you will either get lost as they rush to keep up to you or will be slain by your own hand as you get deeper. Their constant presence has a maddening effect on you as a player, turning on them is a reflex borne of frustration and boredom, as there is not much else to do in the caverns but walk and kill.
The tribes you encounter in the depths will not harm you, you can sleep near them but they may relocate their camp in the meantime so they are not a guarantee of safety. If you desire you can recruit them, although they have a more unhinging influence on you than do companions from the surface, their namelessness and sheer number you can have following you being most estranging.
The underground is a place to be alone, you must come to terms with its mannerisms or your character will not survive it, dying, getting lost or simply getting abandoned by you the player are fates you must accept as inevitable.
Save-scumming is for the weak, if you have no permanent crippling injuries you are not trying hard enough.