These NPCs are hostile to the nightriser faction. They do no move to attack, but they prevent undead PCs from resting in the Sanctum area.
NIGHTRISER FACTION IS BACK?!
This is actually the case with all standard nightriser spawns, such as guardians, warriors, commanders, warlocks, and archers. However, when I approach them within vision range, the standard spawns appear to set me to friendly. This also sets me friendly to the guardians. A brief bout of lag seems to follow the first such contact each reset.