[SixOfSpades]

Ways to leave the Underdark:

1) Perform Adalon's quest (the quick way). After talking to Adalon, go to Ust Natha, kill everything that gets in your way, and return what Adalon wants. Once Adalon is happy, you will be transported to the Exit. This will prevent you from getting any EXP or items from the Ust Natha quests.
2) Perform Adalon's quest (the long way). Do all the Ust Natha quests, and eventually you can obtain what Adalon wants. Once Adalon is happy, you will be transported to the Exit.
3) Do some of the Ust Natha quests, and then kill the Matron Mother Ardulace. This will break the seal on the Exit doors, and then you can go to the Western Tunnels (NOT marked on your map) and make your way to the Exit.
4) Kill Adalon. You will loot a scroll that will break the seal on the Exit doors, and you can then leave as described above.
5) Have a high Charisma. After talking to Adalon, you can make your way to the Exit, and convince the Drow guarding the doors to open them and let you through. This will prevent your getting any items or EXP from any remaining Ust Natha quests.

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All non-essential Underdark quests, such as the Eastern Tunnels, the Southern Tunnels, the Imprisonment crystal, Vithal the Mage, the Kao-Toa Prince, and the Demogorgon statue can be left until later: Simply return to the Underdark via the path you used to escape.