Kill eight non-agro a grey geode (for example at ( -836, 11, -1153 ) Copy/waypoint -836, 11, -1153 or ( -892, 10, -1213 ) Copy/waypoint -892, 10, -1213) On death, each drops a crystal core. Right-click and "Gather crystal core" for the update.
Note: combine that step with the Quest Deep in the Lost Shadows, but remember to hit the Grimlings at least once before using the vial so that you get credit for both quests