In The Cathedral, in one of the naves, you can find a dog called Charlie.
This is Lord Arhu's dog. Speak with her and you learn that someone threw her ball out of a window in Arhu's private quarters.
Your task is to find this ball. Go to Arhu's private quarters. You can break in or teleport your party on a balcony.
The ball is located on a stone ledge under the balcony.
The only way to reach that ball is to use Teleportation. Teleport one of your party members and pick up the ball. Then, you must go back to Charlie and give the ball back.
Reward: 96,950 experience points