After speaking with Professor Kenric, he will ask you to follow the river to the north and look for spires. As you approach each spire you will encounter groups of Hakkonites. You don’t need to kill these if you don’t want to; just trigger the recognition of the spire and continue along the river to the next one. After the fourth spire you will need to follow the path up a hill, and then north over a bridge. Continue north to reach the entrance of an ancient ruin, where you’ll encounter a group of Hakkonites. A Champion will be among them, so you’ll need to spread out to ensure that you’re not hit by their devastating Area of Effect attacks.
When you’ve killed the Hakkonites in the courtyard, interact with the bench near the entrance to the ruins to wait for Professor Kenric and Scout Harding. When you enter the ruins you’ll encounter a puzzle on the floor. You’ll need to step on the correct platforms to open the way. Pulling the lever behind the platforms will reset the puzzle. See the screenshot below for the correct platform order, with 1 being the first platform to stand on, and 5 the last.
Note: Be sure to loot the chest and examine the Tevinter Carving in the room to the east before you proceed north.
To proceed beyond the magical barrier to the north, head east from the barrier along the walls of the ruins. Here you will find veilfire, which you can pick up and take to the barrier to dispel it. Once inside, a cutscene will follow. After the cutscene you can pick up a veilfire torch to uncover two runes on the walls within the chamber.
Once you’ve activated the runes, head back along the walls from the wooden planks to the left outside the chamber. You’ll find a lever at the opposite end of the walls. Pull it to grant access to the trail markers, which you can activate starting with the one atop the stairs in front of the chamber. From here, follow the map icons and activate each trail marker to complete the quest.