Once you get to the cauldron site, fight off the Eclipse troops outside and then enter the excavation.
There will be more Eclipse troops inside and machines as well. Take them out to clear the path and continue exploring the excavation.
Go to the Cauldron Core
Once you reach the cauldron core Eclipse troops and machines will come after you to protect the core. Clear them out and them override the cauldron core
After overriding the cauldron core, you now have to exit the cauldron. Jump on the cauldron platform that you would normally override in other cauldrons. On the right of the Core to jump your way out to the wooden platform. There will be several cultists on the way out. Some of them will be hiding in the tall grass and there will also be Stalkers in the area as well.
Exit the Cauldron
Clear the path as you exit the cauldron. There should be more enemies waiting for you when you get back outside. Just kill them and you should complete the quest.