The wards on the wall have been disabled but the wall is still guarded by the Hakkonites.
- Follow the river and look for spires
- Follow the spire path to an ancient ruin
- Clear Hakkonites from the ruin.
- Wait for Harding and Kenric to arrive.
- Investigate the area.
(There is a pattern by a switch in the courtyard. If you start at the opposite side from the switch and number them like a numberpad, 1 being upper left, 9 being lower right, the first pattern is 8, 6, 2, 4, 5. That opens one door. Then immediately go 8→6→2→4→5→3→9→7→1→5 which opens the 2nd door. The switch resets the floor pattern if you made a mistake crossing the stones. Don't reset after doing the even ones, the middle needs to stay lit for the odd numbers in order to complete it.
- Find a way to take down the barrier. (There is veilfire on the battlements. Get veilfire, carry it to the barrier. An option appears to dispel the barrier. Dispel it.)
- Explore the chamber.
- Look for more clues. (Two runes inside the cavern found using veil fire.)
- Activate a trail marker. (Starting with the lever you get to by following the planks on the left of the stairs, halfway around the square. Then pull the one at the top of the stairs.)
- Light all the trail markers. (Each one is another lever you pull that points to the next lever.)
- The quest completes upon activating the last lever.
- Even when following the numbers precisely, the second door will occasionally not open. This can be fixed by following the instructions in the video linked above. After finishing the first pattern, the only stone that should still be lit up is the middle one (#5). If the middle stone is not lit up, or there is more than one stone lit, then repeat the first pattern until you get the desired result. Then proceed with the second pattern and the second door should open.