This Quest is the way into Farsight Tower Interior. The entrance is at (6977, 6570). Use the Seal of the Eth Kings at the entrance to enable you to pass through the flame curtain blocking the doorway. Enter and go up the steps, then ride the disk up to the top to find the three stones and the flame. When you click the flame, Dargal the Pyromancer will appear and attack you.
When it is time to leave, you still have the Seal of the Eth Kings and will probably need to use it again to pass through the door.
On the level of the bottom of the lift, on the left, is a book for your collections, The Mirrorstones, which tells a story about the last custodian of the stones.