Fiend

A fiend was an evil creature from one of the Fiendish Planes, also called the Lower Planes in some cosmological models. They were not just evil, but born of evil; primal malevolence was one of the roots of their nature, and the evil essence of the fiendish planes permeated every part of their bodies.
Fiends lived long, and some had an inhuman view on time and life. They were capable of viewing a century passing by as inconsequential. Relationships The demons and the Devils held an eternal enmity for one another as they waged the Blood War.[5]
True Name Every creature had a true name that made it possible for other creatures who knew it to gain control over them. For fiends, the true name was a double-edged sword. Knowing their own true name made it possible for a fiend to rise up the fiendish ranks, something that was very difficult for fiends without that knowledge. On the other hand if knowledge of a fiend's true name somehow spilled out, it granted other creatures control over them. This control extended very far. For example, a mortal knowing the true name of a fiend could not only call it from the Lower Planes to the Prime Material Plane but also force it into servitude. Fiends could inconvenience or torment their rivals by helping mortals discover their rival's true names.
As mentioned above, a fiend needed knowledge about its true name to rise up the fiendish hierarchy. It often happened that the true name became different on changing form. It was believed that this was not the true name changing but some form of evolution of the true name. The core of the true name remained the same but there were some additions to it. When a mortal used an outdated true name to bind a fiend, the fiend responded to the binding. However, the control the mortal exhibited over the fiend was not complete and could have fatal consequences for the mortal.
The most important event in the history of fiends was the Blood War. The Blood War was an interplanar battle between demons and Devils, which cost many lives. Thus, both sides were forced to figure out how to rapidly refill their ranks. The answer both sides came up with was to utilize larvae, which souls of evil mortals would become upon death. As larvae would turn into fiends, these fiends could be used to bolster the ranks of either army. Because of this, both demons and Devils started to work towards turning mortals evil.

Genetic Descendants

• Demon
• Devil