Arch Dornan is a drill sergeant in the Navarro base. Equipped with advanced power armor and a characteristically bad attitude, he is the bane of privates, chastising them for the slightest mishaps and breaches of protocol, especially if he dislikes them.
Talking to him even while equipped with advanced power armor will end with him forcing the Chosen One to stand guard at the hangar. If dialogue with him is initiated after being sent to guard the hangar, he will react negatively.
Should he spot the Chosen One out of Enclave armor, there is a chance he has them thrown off the base, thinking they are just another civilian. If spotted a second time, he concludes that the Chosen One is actually a spy and raises the alarm. However, with enough points in primary and secondary statistics, one can fool him into believing that they have actually lost their issued set of power armor or were not issued one by sloppy base personnel, resulting in a lengthy speech and a dismissal to the Quartermaster for another suit.