The Devouts were the followers of Kai's father and his most trusted aids. They had immense strength and an equally immense belief in that man to the point where Kai wouldn't be surprised if they thought of him as a god or at least as a form of god on earth.
If there was an urgent situation, these people were deployed to deal with it and their success rate was 100% which meant that they had never failed a mission before in their lives. That was something even Kai could acknowledge since well, his trainer ever since he was a small toddler was one of these Devouts.
Even more than that, Kai had seen how brutal these men were before. A few years ago, some people in the city rebelled against his father and so this group was sent to capture them.
The mission was so easy that even Kai knew from the start that these people who wanted to rebel were simply done for. He knew that their reason for rebelling was the system this whole city was built on.