This quest is activated by examining "A Glowing Stone". This item is dropped by monsters in the Commonlands.
The quest grants access to a mini-instanced zone. This instanced zone is populated with a few groups of level 15 monsters and is accessed by clicking the stone behind Zarvonn's Tower in the Commonlands.
Once you zone in the quest closes and you can not zone in again, without finding another stone. The reward is the loot tables inside, which are quite good for the level range.