Forest of Tethir Overview - Baldur's Gate 2
The Forest of Tethir is unlocked during Chapter 6 , you can access this map by traveling through Small Teeth Pass then North Forest. On this map you will find the path that leads you to Suldanessellar which is the elf town and first map of Chapter 7. In order to unlock the route to Suldanessellar you will need to defeat Bodhi and retrieve the Rhynn Latern. Only after you've obtained this item will you be able to "light" the path (get it?).
Aside from Suldanessellar the other 2 unique things about this map are a Cave which contains Mana Bow +4 and a mini event between Coran and Safana. If you played Baldur's Gate 1 you probably remember these 2 as potential companions.
Cabin: Inside the cabin you will be attacked by various ghost enemies but they shouldn't be too hard to defeat. Search all of the containers in this building to find a lot of magical ammunition as well as Longbow +1, Wand of Lightning, Chain Mail +2 and Large Shield +1.
Coran: Standing outside of this Cabin you'll find Coran who will stop you and speak to you the moment you get into range. He asks you for help rescuing his lover, Safana, who has been captured by wolfweres. Once you speak with Coran and start this event you'll be able to find Safana in the middle portion of the map around where we entered.
Cave: Inside this cave you'll find Mana Bow +4 along with some magical ammo.
Safana: Safana will only spawn here after you've spoken to Coran outside of the Cabin and begun the Coran and the Wolfweres side quest. There will be a little scripted event here that will result in her death after which you'll have to battle it out with the wolfweres. When Coran dies you'll get a Short Sword +1 and Leather Armor +1 but other than that only gems and gold drop.
Suldanessellar: Here is where you will find the entrance to Suldanessellar, the elven town. The route to Suldanessellar is blocked until you obtain the Rhynn Lanthorn by defeating Bodhi in her lair during Chapter 6. Check out my Chapter 6 Walkthrough for more information about how to open the path to this town.