This objective is very simple just as you did in the Dig Site, you have to clear the 3 camps of the cultists. You can take them out anyway you want, stealth or straight forward but once the enemies detect you, the Nora tribe will aid you making it easier to clear each camp.
Go to the Tallest Tower
After clearing all the camps, you will need to talk to Sona. Follow the quest marker and go to the tallest tower. She will discuss about the Metal Ring and Varl will accompany you there.
Enter the Metal Ring
Follow Varl to the Metal Ring and search for a view of the Blaze containers. The objective is very simple and all you have to do is follow Varl, listen for who to kill and perform some sneak attacks on your enemies. At the end of the path a cut-scene will start giving you a view of the Blaze containers.
Shoot the Blaze and Kill your enemies
Now you will have to shoot the Blaze containers. There will be some Corrupted Machine in the area and a lot of cultists. Stealth without killing anyone is your best option but you may also engage the enemies if you want to. Once you get to the Blaze containers set it on fire with fire arrows. A short cut-scene will occur and then you now have to kill all the cultists and Corrupted Machine along side the Nora tribesmen.
The quest will complete after the cut-scene and you must now prepare to travel to Meridian for the next quest: The City of the Sun.
This quest is complete crap. Cultists just spawn infinitely and even headshots alert the others.