[ Disclaimer, Create new user --- Wiki markup help, Install P99 ]
Charasis Basemement
Charasis/Howling Stones Basement
To get to the basement simply drop down from the entry platform, ideally off the north end. A high-level character (55+ at least) should be able to survive the fall, but of course Levitate or Dead Man Floating will save you HP.
Entry/Middle Room
Unless someone has cleared the room there will be 4-5 mobs up and wandering about, but there is a safe spot where you can land (and pull from): the raised ledge on the North end (where the above picture was taken from). Almost all of the mobs in this room are melee, with one exception: An undead oblation. You should also be aware of the Sepulchre Skeleton, as it is a Shadow Knight that will harmtouch.
If you pull carefully you should be able to kill all of the mobs in the room one at a time. After you're done there are two side rooms, which connect to further corridors. None of these have especially great loot, but it's a great area to gain XP in, especially if you're a soloing Enchanter/Necromancer/Shaman, or a group when the wings above have already been taken.