Fire Hellion

Fire Hellion
To my mind, the fire hellion perfectly illustrates the difference between natural fire and the corrupt flames of the Nine Hells.
Fire giants study war in its many forms across the multiverse, which sometimes leads the giants to a fascination with the Blood War—the endless conflict between demons and devils across the Lower Planes. Such a giant might enter into a pact with a powerful devil, hoping to learn tactics the devils have fine-tuned over millennia and to acquire magical gifts to help the giant rise in the ordning.
Over time, the giant is corrupted, becoming a Fiend in its own right. The devil teaches the giant how to forge with infernal iron and hellfire, enabling the giant to craft weapons that can funnel the souls of the slain to Avernus, the first layer of the Nine Hells. In this way, the devil stands to gain a constant supply of souls from the giant's enemies, as well as the promise that the giant will serve the devil as a smith in the Nine Hells after death.
The corrupted fire giant takes on fiendish features, including horns, cloven hooves for feet, and a forked tail.