Fiend

A fiend was an evil creature from one of the Fiendish Planes. 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 permeates every part of their bodies.

Demons
Demons were the most widespread race of fiends. They were chaotic evil and were native to the Abyss. Tanar'ri, obyriths, and loumara were the three races of demons, but there were many other species as well.

Yugoloths
Also known as daemons, yugoloths were manipulative, neutral evil fiends native to the Blood Rift. They were secretive and mercenary by nature.

Devils
Devils were lawful evil fiends who hailed from Nine Hells of Baator. The baatezu were the dominant species.

Demodands
Also known as gehreleths, demodands were said to have been fashioned by one of the primal creations of Evil, exiled because of their chaotic taint. They dwelt in the Supreme Throne.

Archfiends
Archfiends were not actually a separate kind of fiend on their own, but rather a grouping of powerful, unique fiends of any of the above kinds. The most prominent groups were the archdevils and demon lords. Archfiends could be incredibly powerful, almost as powerful as true deities.

Half-fiends
Due to their magical natures, fiends were capable of breeding with most other creatures. The resulting offspring was called a half-fiend. Some such hybrids could breed true. Notable varieties of half-fiends included cambions, fey'ri, and draegloths.

Other Fiends

 * Hell hounds- Fiends that looked like large, powerfully built dogs with rust-red fur, red eyes, and black teeth and markings.
 * Barghests- Shapechanging fiends native to Gehenna, barghests naturally resembled large, goblin-wolf hybrids with orange eyes and blue fur.
 * Larvae- Also called soul larvae, larva were the fiendish remnants of evil mortal souls.
 * Night hags- Merciless, horrible humanoid fiends with black skin, red eyes, skeletal bodies, clawed hands, and horns. Night hags also possessed powerful magical abilities.
 * Nightmares- Neutral evil fiends that appeared as large black horses with flame in place of a mane and tail, and flaming hooves.
 * Maelephants- Large, humanoid fiends with clawed hands and elephant-like heads. They were often employed by more powerful fiends as guardians of treasure.

Relations
The demons and the devils held an eternal enmity for one another as they waged the Blood War.