Head to the East from the courtyard that you are in.
Head through the short room to the energy door blocking your way forward. Turn North after that.
You need to dodge through this Hallway and avoid the three sets of ceiling spikes.
Make it to the far end, you will need to deal with even more Thralls. They are defending a central point, a Checkpoint. You will need to clear them out and destroy the Shards nearby to get at the Keystone. Turn to the East to continue. You have more ceiling traps to avoid as you fight through to the next chamber.
This leads to a courtyard with more Thralls crawling all over it. There are Primal Thralls rushing you on the ground. You have a few Thrall Gunners and Thrall Brutes on the ledges above firing down on you. There can be a Thrall Bonecrusher that you need to deal with as well.
Clear out the Thralls and head to the Southwestern corner of the courtyard. You will find a jump pad that will launch you onto the upper balcony of this area.
Follow the walkway into the chamber and then follow the pipe and drop down it to reach the next part of the area.
This large chamber has a number of stationary traps that you can use against the numerous thralls that are about. You have yet more ceiling traps to worry about in addition to spinning bladed pillars.
To get out of this chamber and move forward, you will need to jump onto any of the ceiling traps when they are down. Then head out of the room through the Southwest archway. Clear out the Thralls in the area and go through the archway when it opens.
Head out into the courtyard and Defeat the Guardian Arc.
Destroy the Guardian and wait for the Keystone to rise up from the ground. When it has emerged, simply have the team stand on their switches to activate it.