Getting lost underground?

[Jon_Dahl]

Let's imagine travelling for two days underground (Underdark, specifically) and encountering several junctions and confusingly twisting tunnels.

How easy is it to get lost underground? The rules are fairly specific about getting lost in the wilderness (http://www.d20srd.org/srd/wilderness.htm#gettingLost), but I'd like to set fair "Getting Lost Underground" rules for my game.
(Something like a few easy survival checks would be fine)

[Red Fel]

I would imagine it's much easier to get lost underground, particularly in the Underdark - and much more dangerous.

For one thing, being above ground offers many opportunities to reorient yourself. You can seek out a higher vantage point to get the lay of the land, you can check the position of the sun or the stars to get your bearings, you could look at the type of trees or similar growths to figure out your location. In an emergency, you could send smoke signals or similar communications.

Things change underground. There are no high vantage points (except in the massive underground caverns, but all that tells you is "you're in a massive underground cavern"); there are no celestial bodies to help you reorient. And while there are various growths and environmental cues that might tell you what kind of underground region you're visiting, it's a very different Survival or Knowledge check than most topsiders are accustomed to. Further, don't bother calling for help - what finds you will be anything but helpful.

Now, if you have a character specifically trained in traveling through the Underdark, that's a different story. But as a rule, I would ramp the "getting lost" DCs up substantially. The Underdark is no place for amateurs.

Consider that the survival DC in a forest is 15. 15. Someone with a mere 5 ranks in Survival can take 10 on that check and make it, easy. That's nothing to a trained Ranger or similar character. The Underdark is one of the most dangerous places on the Prime Material; I'd give it a substantially higher DC. I'd give it at least a DC of 20, probably higher - definitely higher in more confounding and labyrinthine areas. This is not a place for low-level characters, and not a place where you want to slack on your Survival skill.

[Fouredged Sword]

Not only that, but it is much harder to get where you want to go in the underdark.

Say you want to go to a city in the overworld. Worse comes to worse, you determine north and head in the correct direction. You can look for habitation and ask for directions as you go, and if you run into a uncross-able area, you go around until you find a path.

In the underdark, there is no way to just head north. Without preknowledge of HOW to get where you are going, it is almost impossible to get there. Going north may mean taking the south passage of a tunnel, with no way of knowing that unless you had a map. You can't find a town to ask for directions unless you stumble literally into the middle of one, and the town is far less likely to be friendly. Rather than finding your way around impassable areas, there is likely one single passable path that you have to find, and if you miss it, you cannot get where you are going.

That and the monsters are more likely to eat you.

[HammeredWharf]

I think I read that you can use Knowledge (Dungeoneering) instead of Survival when navigating caverns and such. I have no idea where, however.

[Jon_Dahl]

Good posts so far! Thank you Fouredged Sword, it seems that you are like my smarter twin brother :D

If we narrow all this down to a simplified rule, how about this?:

Check once per hour (or portion of an hour) spent moving in the Underdark to see if travelers have become lost. In the case of a party moving together, only the character leading the way makes the check. Check is not necessary if there's little or no junctions. It's possible to travel for days in the Underdark and not get lost if there are very few junctions. In such cases getting back is rather straightforward.

The default survival check DC is 20, and DC 25 for especially confusing tunnels with several junctions.

A character with at least 5 ranks in Knowledge (dungeoneering) gains a +2 bonus on this check.

[Jon_Dahl]

So I think we have a consensus here :)