Neferon

Neferon was an Arcanaloth who resided in the Amber Temple, a long-forgotten sanctum of dark knowledge hidden in the Balinok Mountains of the Zarovich Valley. Unlike most of his kind, who preferred the chaos and commerce of the Lower Realms, Neferon had opened himself to the possibility of contacting the Prime Material. This unwittingly resulted in him living the rest of his existence as a slave; he unwittingly answered a summon by the mages of the Azure Paragon, not realizing the terms he was bound to. In permanence, the arcanaloth was contracted to protect the Temple from any creatures who sought the Dark Powers that lay within, but forbidden to attack any members of the Paragon.

Neferon was bound to the Temple inside Mount Ghakis, and was unaware of the Azure Paragon's fall during the Pre-Unified Age. For thousands of years, he was unable to leave, until the Count Strahd von Zarovich visited the temple out of curiosity. Neferon had became bored, jaded, and somewhat crazy, with few creatures visiting the hidden redoubt. Having already fully read through the temple's manifold manuscripts and secrets, he welcomed the charming Count, who visited on a search for arcane knowledge, rather than a dark bargain.

Not bound to fight someone who had not come to seek a Dark Power, Neferon allowed Strahd access to the Temple, accompanying the Human and teaching him about magics. This, however, was ultimately an error: Strahd opened a vault containing the amber sarcophogus of Vampyr, and unknown to Neferon at the time, made contact with the Dark Power. Though Strahd's witnessing of the sarcophogus would eventually result in the Wedding That Never Was, and the ousting of the valley from its native Realm, he successfully convinced Neferon that he was uninterested in the them.

Years later, Strahd would visit Neferon as a powerful Vampire Spellcaster, having invoked a pact with "death" to keep him eternally young. He had learned about the arcanaloth's abilities; powered by Vampyr's undead magic, he narrowly defeated Neferon in combat and made his way back to the vault he had visited years earlier. He proceeded to destroy his patron's sarcophogus, releasing Vampyr, and the Dark Power ripped Strahd's dominion from the world and into the Umbral Realms. 

Vampyr's new Demirealm altered the nature of magical communication, allowing Dark Powers to contact creatures within it and manipulate the land with subtle magics, though not nearly to the scale that Vampyr enjoyed.  Whether out of mercy or amusement, Strahd kept Neferon alive, but he was still bound by ancient oaths and forced to fight those who sought Dark Powers. Despite his natural aversion to combat, Neferon killed many adventurers in the Amber Temple over hundreds of years, called there by various Dark Powers. He collected their items over the years, one of which was Sergei von Zarovich's Bright Blade, but had little interest in a sword of sunlight.

In time, Neferon was visited by an equal match, an archmage also trapped in Barovia named Orlev ben Khazan. Khazan was the constructor of Castle Ravenloft and sought to become a Lich; Neferon allowed the wizard to roam the temple, as he was not swayed by Dark Powers, but watched somberly as the man failed his transformation. Khazan lost his soul, then his mind, becoming a sort of eternal librarian that stalked the temple halls and made dangerous traps and monsters to protect it at Strahd's behest. Patrina Velikovna followed, seeking to learn in the same manner that Khazan had, and Neferon permitted her to learn from the decaying lich for decades.

Strahd himself, however, was now significantly more powerful, and at Patrina's recommendation would make many visits to the Temple. Fearing death, Neferon found a way to not fight the Vampire: though Strahd was now a champion of a Dark Power, Vampyr had already been released, so long as the Count was not seeking to break any other sarcophagi, Neferon was not bound to defend the temple from him. Instead, Neferon hid from Strahd, an act that the vampire lord found amusing.

Following Patrina's death, the Count eventually stopped visiting the Temple, leaving Neferon and the broken Khazan to stew in immortal boredom. He would return hundreds of years later with the arrival of The Abbot. The two watched as Strahd defeated the Deva and took him to Vampyr's broken sarcophogus. Dark magic surged from the tomb and poisoned The Abbot's mind, adding him to Strahd's pantheon of powerful playthings, and Neferon continued his work as normal.