Umar Hills Overview - Baldur's Gate 2
Umar Hills is one of the lower level maps in this game and a great area to hit up for EXP and money during Chapter 2 & 3. You can unlock this location on your World Map by speaking with Delon in the Government District of Athkatla and accepting the Investigate the Deaths in Umar Hills side quest from him. Alternatively you can also speak with Tolgerias in the Council of the Six building (also in Government District) and accept The Hunt for Valygar Corthala quest. Both of these quests will add Umar Hills to your World Map and allow you to fast travel there.
There are 2 companions you can find that are connected to this map; the first is Valygar Corthala who you can find in the northern portion of this map. Next is Mazzy Fentan who you can find in the Temple Ruins map which is unlocked by progressing far enough in the Investigate the Deaths in Umar Hills side quest.
Mayor: You'll be visiting this house a few times during the Investigate the Deaths in Umar Hills quest. When you first arrive in the village you'll need to speak to the Mayor and you'll also have to speak to him again after talking with Madulf in the north and after solving the issues at the Temple Ruins.
Jermien: Inside this house you'll find a Cowled Wizard by the name of Jermien along with his daughter and a golem that he is working on. If you ask Jermien about the golem then he'll offer the Find Mimics Blood for Jermien side quest to you which is a quick way to earn some extra EXP.
Fael: At first Fael appears to be just a normal vendor but he's actually the quest giver for the Finish The Leather Armor begun by Rejiek Hidesman quest. Head over to that quest entry page for more information about how you can begin the quest and what is involved in it.
Group of Kids: Your first time walking by this location you will be approached by a group of kids who will ask you to buy them some Ale and 3 Bastard Swords. If you agree to buy either of the 2 items for the kids you'll begin the Idle Hands in Imnesvale side quest.
Madulf: During the Investigate the Deaths in Umar Hills quest you will be tasked with speaking to Madulf about the murders and disappearances happening in Umar Hills. Madulf isn't responsible for everything happening in town and will actually ask you to speak with Mayor Lloyd on his behalf and ask to establish a trading relationship. I recommend you do this short side quest as it'll reward you with some decent EXP.
Umar Cave: The only notable thing inside of this cave is a treasure chest which turns out to be a Mimic. After defeating the Mimic be sure to loot the Mimic's Blood from the body so that you can complete the Find Mimics Blood for Jermien quest.
Valygar's Cottage: Inside this building you'll find Valygar, a potential companion in BG2. He is required to open the Planar Sphere dungeon in the Slums of Athkatla and is part of the The Hunt for Valygar Corthala quest. When you first approach his building you'll be stopped by a group of rangers who you can battle for some extra EXP if you wish.
Ranger Stronghold: You have to visit this building during the Investigate the Deaths in Umar Hills quest in order to unlock the Temple Ruins location on your World Map. Inside the building you will have to loot Merella's Journal as well as A Note from Mazzy Fentan. These 2 items will give you the quest updates you need and mark Temple Ruins on the World Map. Once you complete this quest you'll also be able to take over this building as your Ranger Stronghold - if you're playing a Ranger class.