Steel graves, golems, and revenants
Mod mepha here to elaborate on one of the concepts mentioned earlier, walking power armor.
During the brotherhoods attempted siege of Florida had taken over the Kennedy space center as a base of operation, the space center having been converted into a nuclear launch site during the Great War. Due to this being the only brotherhood base, and then being far off from other brotherhood bases, they had to keep tabs on all their equipment, mostly power armor. Similar to the trauma suits in old world blues, the power armor of the brotherhood was fitted to operate on its own if its occupant was injured, carrying it back to the base and attack anything dangerous.
Well when the Native tribe attempted to push the brotherhood out, they accidentally set off an EMP and caused the suits to lock up, preventing the wearer to escape, and viewing everything as a hostile target. Essentially, brotherhood paladins became trapped inside the suit, unable to move as the suit began attacking and killing off the brotherhood.
The suits of power armor still roam, some empty, some with its dead occupants still inside. They will attack anything that moves and can be extremely powerful, but most have rust avd water damage, making them a bit slow.
Golems are empty suits of armor.
Steel graves are suits of armor who's occupants are dead and in advanced stages of decay.
Revenants are suits of armor contains skeletal remains.
Story and concept liable to change