The Caeus Acritas are an elite league of Harnessers who are used to maintain peace within kingdoms. When referring to them individually, one would use the term "officer." They originated exactly one year after the Great War as a means to quell riots and rebellions against the kingdoms they work for. Most kingdoms have their own leagues of Caeus Acritas, and the way to differentiate one kingdom's officers from another is to look at the color of their arm bands. Praxis ' officers, for example, wear grey arm bands.

The Caeus Acritas answer only to their kingdom's leader. They are known to travel in pairs or groups of four and share a worldwide reputation for being ruthless. Some kingdoms use their officers to spy on other powers, or track certain people down. They have a so-called streak of perfection, which entails that they don't fail any job given or allow any lawbreaker to go unpunished. They are only ever seen out and about in the night. The mask they wear is made of a morphing fabric woven from special thread that is more often seen as a hood than the mask for practicality's sake.