Go to Ab'Dendriel. Go up one floor in the depot and head west. Talk to the NPC Eroth about a mission. He will say you have to destroy an orb in the top of the tower of Elvenbane with a Mirror.
Player: hi Eroth: I greet thee, outsider. Player: mission Eroth: Have you ever heard of Elvenbane? It is the castle west of Ab'Dendriel which is inhabited by villains from all over the continent. Any support in this war is welcome. Are you willing to help? Player: yes Eroth: Recently we found out that they are in the possession of a scrying crystal ball. They can hear all our discussions about tactics and upcoming attacks. ... Eroth: No wonder that they always have been so well prepared. Now you come into play, destroy the scrying crystal ball in Elvenbane. It should be on the top floor. ... Eroth: We don't really know how to destroy it but we suppose it may work if you reflect the invisible power of the ball. The beam should be adjusted to Ab'Dendriel. Take this mirror and give it a try. Good luck.
Player: hi Eroth: I greet thee, outsider. Player: mission Eroth: I heard the blow! The reflection must have caused a overcharge of magical energy leading to the contraction and the implosion. Just like I hoped! Please take this as a reward. Thank you very much.