Originally Posted by Adiktus
I've found four ways into the UD so far. The Selune Temple route seems to be the easiest, and the earliest one you'll come across if you play the way the game is designed to push you (ie you don't know all its secrets inside out). I was talking more about multiple options for solving *immediate* problems, so if you're in the temple, you have at least two ways to progress.
The first entrance I've found on my first playthrough was the spider cave, but I didn't use it because I was afraid it would be a one-way trip. But once I've learned that flying creatures don't take fall damage, I've sent a raven familiar down the cave. If you have an imp you could have it go invisible and won't even have to fight the spiders. And then you can just use it to find a waypoint in the Underdark, so I find it easier than the temple.

I think failed perception checks should not be revealed, though. It's a bit immersion breaking: you as the player know there is something there, even though the party doesn't. And also the reverse: I think for quest items like the soul coins there should be a perception check, because as it is now, it is the player that has to spot them.