You'll get this quest when you reach level 5 and talk to Griswold. He will tell you a tale about a caravan that was carying a piece from the heavens. Then some cloaked dudes and ambushed the caravan. When Griswold searched for the rock, he didn't found it. Now it's your job to find it. This is easy, you should find the rock in level 5 or 6 laying on a table, grab it and take it to Griswold. He will make an excelent ring from it, The Empyrean Band. Use it, its very good.