Southern Tombs Overview - Baldur's Gate 2
The Southern Tombs is a small zone that is reached by traveling south off the Lower Tombs map. You'll be visiting this map during Korgan's Companion Quest along with during Edwin's Companion Quest. Other than the objectives for these 2 quests there is not much of note on this map.
Undead Ambush: The first time you step foot into the center of this room all of the tombs nearby will open up and undead will come spilling out of them. All of the undead are pretty low level so you shouldn't have much trouble with them though. One thing worth mentioning is that there are many traps you can find throughout this room hidden on picture on the floor - be careful while fighting the undead lest you set off all the traps!
Book of Kaza: You'll have to visit this location with Korgan in your party to complete the first part of his companion quest. For more information about this quest check out my Help Korgan Recover the Book of Kaza side quest entry.
Nevaziah: At this location you'll meet a Lich named Nevaziah assuming that you've started Edwin's Companion Quest. If you're not currently on this quest with Edwin then there will be nothing really of note in this room.