I managed this deed on a lvl 106 ‘toon. – take a mission stable horse to Akraz-Zahar, about face and go out the door. Mount up and go to the end of the corridor, turn left and go down the stairway. About face (east) and leave the homesteads then turn right (south) and leave the Hall.

When you leave Erebor, turn right at the bottom of the last set of stairs and follow the cliff wall west and north all the way to 29.4N, 28.5W. I’ve started a trail of red flags there. Follow the red flags until the sky turns orange. Look for a book page on the left and look to the right to see the door. Go to the door and click on it.

Before you leave, there is a treasure cache at the northern end of the path – at the edge of the cliff.