Tiaral

I bet there’s a whole industry dedicated to this. Kids go to universities or slave-trading courses, where they learn how to make drugs and design devices. There are factories in the city that supply millions of slaves with their devices. Some of them are exported to other countries. Each slave is equipped with a device as part of the purchase by another person. Newer models of the master's bracelet can be voice-activated to control up to ten slaves at once, so you don't have to use all your hands and feet.

Well, he could have tamed him using another Heckelian artifact – master and slave bracelets. The effect is obvious, with a small caveat that the second bracelet must be worn voluntarily, but it is not necessary to know what effect it has.