Tyranthraxus

Tyranthraxus, also called the Possessing Spirit and the Flamed One, was a malign entity who stole control over the bodies of others to further its wicked goals. He was said to have been one of the Seven Lost Gods forced long ago to bow before Bane. Some sages have identified him as a type of yugoloth, though spells normally effective against such fiends have been shown to have no effect on him.

All that is truly known is that Tyranthraxus was an extraplanar entity of unknown origin but apparently (according to the creature's own diary), a very weak example of his kind.

History
Some sages have said that Tyranthraxus ruled over a large swathe of land consisting of the Moonsea region and northern Cormanthor in an unknown time before the Dalelands were settled by humans. He had 3 lairs during this time: One in the Dragonspine Mountains, one in what is now Yûlash and one in what is now Phlan. He came into frequent conflict with the elves of Cormanthor and was also known by the ogres of Thar. He was driven out of Yûlash by followers of Moander wielding the Gauntlets of Moander and his rule was ended by someone wearing the Helm of the Dragon (which showed his true form when he was in possession of someone) and the Blade of Lathander, a holy sword said to have been forged specifically to slay him. Over the years, many tales of possessing spirits have been told but it is impossible to determine which, if any, actually involved Tyranthraxus.

The oldest of these legends of Tyranthraxus were those of the ogres (once known as the beast-men) of Thar. They claimed that, long ago, Tyranthraxus was a powerful general who lead "the Riders out of the Waste." In this form, he conquered the ancient kingdoms of Barze, Horreb, and Vane. While temporarily bodiless, he was imprisoned by one Baron Schodt in a vial of shining water which sank beneath the depths of Lake Longreach.

The Kingdom of Barze was overrun by Tyranthraxus and his Twisted Ones in -356 DR. Some say the Dark Three had a hand in setting Tyranthraxus against their former allies in Barze.

At some point (possibly before the conquest of Barze), Bane (and likely his comrades Bhaal and Myrkul) apparently encountered Tyranthraxus during their quest for immortality and forced the Flamed One into servitude.

Circa 1240 DR, agents of Tyranthraxus convinced the bronze dragon Srossar to bathe in the Pool of Radiance, convincing him it would grant him greater wisdom and understanding of the multiverse. Instead, it allowed Tyranthraxus to possess his body. Combining his own powers with the immense powers of his host, Tyranthraxus raised an army of orcs, hobgoblins, and similar creatures and stormed into Phlan. For 50 years however, the barrier formed by the Moonsea and the forces of Zhentil Keep kept him from expanding any further. Then he was caught by surprise when Phlan began to be recolonized by humans.

In 1340 DR, Tyranthraxus' rule over Phlan was challenged by the adventurers Shal Bal, Ren o' the Blade, and Tarl Desanea. When it looked like he would be destroyed, Tyranthraxus entered a different body and dove into the Pool, using its magic to teleport away.

Emerging from another Pool of Radiance, he found himself in Myth Drannor 17 years later. Here he quickly established himself as a dominant force over the baatezu and other evil creatures inhabiting the city through a mixture of diplomacy, strategic possessions and playing the various factions against each other. He learned from his new subordinates how to better manipulate these Pools and used the one he'd entered the city from to erect a magical barrier over the city, barring entry in or out.

Later in the year, Tyranthraxus intercepted some members of the Fire Knives guild along with a small group of Moander-worshipers fleeing north from Westgate who told the tale of a woman named Alias, branded by their masters and a few others with magical blue tattoos called Azure Bonds which forced her to do their will. Although Alias managed to break free, Tyranthraxus saw an opportunity to further his own goals by placing these brands on a group of adventurers similar to those that managed to defeat him in Phlan. He gathered the cultists, Fire Knives, a renegade Red Wizard of Thay and a group of Zhentarim mages then captured a party of sellswords to inscribe the Azure Bonds onto. Each faction gave the party a compulsion but none realised that it was possible for the group to resist them.

Unfortunately, the adventurers proved more resourceful at breaking the Azure Bonds than fulfilling their compulsions and with the help of Elminster to open a hole in the barrier surrounding Myth Drannor, used the Gauntlets of Moander, Helm of the Dragon, and Blade of Lathander to slay Tyranthraxus in his lair.

Physical description
Tyranthraxus took the body of whoever he was possessing and avoided changing its appearance too much in order to avoid suspicion.

Abilites
The Possessing Spirit could cause his stolen body to erupt in a fiery aura. He could read all thoughts within his line of sight and accurately mimic the voice, gestures, and posture of the one whose body he was inhabiting. If not in a body, he was able to sustain himself within any magical liquid, though it is not known how long he could last outside such a medium.

Personality
He was cruel, ruthless, and intelligent. Tyranthraxus was a meticulous record-keeper. He liked to keep written records of every significant action, his conquests, his subversions, every creature under his control, what resources he could command, etc. Being in a body that was incapable of writing was rather frustrating to him. He also felt humiliated whenever he was forced into the body of an animal, having to flee from larger animals and unable to communicate.

Goals
While in the body of Srossar, Tyranthraxus' goal was to control the mind of every living creature on the Material Plane, a goal he believed he could achieve with the Pool of Radiance, six ioun stones and blood to fuel his own life energy. He had managed to collect four ioun stones when he encountered the adventurers that would kill his body, and attempted to get the two stones that Ren carried to complete the set, pretending to be Srossar, set free from his own influence. The party however, saw through his lies though and foiled his plan.

After he found himself in Myth Drannor, he felt vulnerable, being forced into the body of a human after so long in the mighty body of a dragon. He put his plans of mass-control on hold and instead sought the destruction of the three magic items that could destroy his true form.

Relationships
Tyranthraxus's enemies included Shal Bal, Ren o' the Blade, and Tarl Desanea. He was the most powerful member of the New Alliance.