Once the mutagen canisters are rigged, head to the Free Drones under-passage base in Lower Underrail and rendezvous with the CAU. You can find it in the under-passages just south of Rail Crossing's entrance.
The area where you meet up w/ CAU is an uncontrolled zone. I managed to kill Dess and Void by luring them into a mine field using noise w/o triggering hostility w/ Protectorate. When I returned to talk to Captain Mareth I get this:
https://i.imgur.com/h1Mcqt3.pnghttps://i.imgur.com/dmLxTWL.png
