Yolheimsu'um

"I am fire. Fire burns. It consumes. It destroys. But it can also temper when applied carefully—if the material tested is strong enough."
Yolheimsu'um the Forge Wyrm is an adult red dragon who lives in the duergar city of Brazenthrone, keeping the city's forges alight in exchange for food and treasure. His physiology is unusual for a red dragon, having been altered by a lifetime of exposure to the Underdark's unique magical energies, and bares different bodily features and green fire breath unlike that of his kin found on the surface. It is thanks to Yolheimsu'um's fiery breath that Brazenthrone's armor and weapons are considered to be the best in the Underdark, having been forged in dragonfire. He is attended by a group of duergar Tiamat worshipers known as the Bellows, who view Yolheimsu'um as the Dragon Queen's representative in their city and answer to no one but him, not even Deepking Oghren Orzammar III.

Early History

It is unclear exactly how a red dragon like Yolheimsu'um wound up in the Underdark, so far from the type of territory that red dragons typically choose to inhabit. His unique physiology would indicate he's likely been in the Underdark and exposed to its unique magical energies for quite some time, potentially since the very day he hatched. What is actually known about Yolheimsu'um's origins can be traced back a mere 250 years.
When the duergar of Brazenthrone were preparing to attack the Tideborne Tribe, they used Charwell Fortress as a staging ground. Yolheimsu'um watched these proceedings eagerly, planning to destroy the weakened victor of the conflict and lay claim to anything worth adding to his horde. This conflict did not come to pass when the Sword Dancers allied with the Tideborne Tribe, causing the duergar to pull back and cancel their planned invasion. But the duergar ships had already depleted much of Charwell Fortress' resources, taking much of its provisions and many of its soldiers for their expected military campaign. The ships sailed back to their home port of Brazenthrone rather than Charwell Fortress, which Yolheimsu'um attacked now that it was underdefended.
It took little effort for the red dragon to raze the skeleton crew defending the fort and devour their remains as he began to sift through the fort for anything of value. He knew that the duergar would eventually send a ship to check on the fort and decided to remain there to ambush the ship as well. Much to his surprise, when the ship did arrive it came bearing an envoy with tribute rather than soldiers. The duergar who disembarked explained they were followers of Tiamat, Queen of Evil Dragons, and considered Yolheimsu'um to be a holy vessel and his coming a reward for their faith. They had come both with gifts and an offer; equal parts intrigued and amused by the little mortals musings, Yolheimsu'um decided to listen to their proposal.
These clerics had already negotiated with the duergar king, Deepking Oghren Orzammar II, and negotiated the outline of a treaty with him. If Yolheimsu'um would relocate to Brazenthrone and allow the duergar to forge mighty weapons and armor in the fires of his breath, they would supply him with a never-ending stream of food and treasure. The duergar went from having Yolheimsu'um's curiosity to having his attention, and the red dragon agreed to accompany them back to Brazenthrone. He and the king struck an accord and Yolheimsu'um has lived in Brazenthrone ever since, alighting their forges with dragonfire and making their works the envy of all the Underdark. The clerics who initially met with him went on to form the Bellows, which continue to serve Yolheimsu'um to this day.

Journey Into the Underdark Arc

Catching a Wyrm's Attention

The adventurers of the Thaig expedition heard of Yolheimsu'um and his history with the region during their time on the Black Loch, several of them wondering what kind of accord the Deepking could have struck to get a red dragon as a business partner. When the group later traveled to Brazenthrone themselves, they had a run-in with the dragon while being escorted through the Anvil Quarter towards the Common Quarter. While most of them stood out of his way, at the behest of his Bellows, and tried to remain unnoticed, K went out of his way to call out to Yolheimsu'um while posing as a follower of Tiamat. He broke off from the rest of his group to watch the Forge Wyrm refresh the flames of the Freehammer Forge with green dragonfire; though subtle, Yolheimsu'um's body language seemed to indicate he had taken notice of K's actions.

Audience with the Forge Wyrm

Late that evening, a member of the Bellows delivered a letter to the adventurers stating Yolheimsu'um had summoned them. One of their fellowship would come to collect the travelers at noon the next day, and the invitation's wording made it clear this was less a request and more a demand. Thinking it unwise to potentially displease a dragon, the group remained in their apartments until Galmin Firechains came to collect them. He led them through the streets of Brazenthrone to the southern edge of the city where worked stone gave way to the natural cave Yolheimsu'um had made his lair.
Galmin took the adventurers past many guards, all Bellows like himself, and around pools of water that were soon replaced by pools of magma. As they approached the central pool, Galmin motioned for them to halt while he approached the edge and banged his warhammer on the ground several times. A wake approached from beneath the magma and Yolheimsu'um partially pulled himself from it, lounging as he told the adventurers to introduce themselves and introducing himself in turn. With the pleasantries out of the way, K (who was making of show of faking faith for Tiamat, Queen of Evil Dragons) asked for what reason Yolheimsu'um had called them here.
The dragon told them that while he was making his rounds lighting forges, someone had slipped past the Bellows and stolen a valuable tome from his horde. Though the had a number of suspects (nobles who were political rivals, greedy merchants, and the renowned thief Diir among them), he'd no idea who he could trust outside his Bellows and they had so far failed to retrieve the item. Since the adventurers had only just arrived to Brazenthrone, they were not suspects and therefore made good candidates for finding the burglar. His wording made it clear that as far as Yolheimsu'um was concerned, they would do this for him or there would be consequences.
K asked what sort of reward they could expect in exchange for this service. Yolheimsu'um stated that they would do it because he told them to and that that was good reason enough. Not taking the hint, K insisted that some additional reward would serve as proper motivation. An angry looking Yolheimsu'um pulled himself fully out of the magma and was on top of K in an instant, telling the bugbear that he was playing with fire that could very easily burn, consume, and destroy him. But, Yolheimsu'um noted, fire could also temper when applied to material strong enough to withstand it. The dragon respected K's boldness and stated he would prepare a suitable reward should the adventurers succeed.
Yolheimsu'um instructed Galmin to give the adventurers badges showing the symbol of the Bellows, Galmin telling them the badges would let them move through Brazenthrone a bit more freely but that the notoriously stubborn guards may still need some persuading. As Yolheimsu'um instructed Galmin to see the adventurers out, he paused to tell Galmin that should the adventurers succeed in retrieving the missing tome first, he would be fired from his position as leader of the Bellows. When the adventurers inquired whether that statement was literal or figurative, Galmin seemed to think it was both.

Punishment & Rewards

Several days later, the adventurers returned with the stolen tome in hand. Galmin, rather than try and race against the adventurers, elected to try and ambush them with his loyalists for the tome at the entrance to Yolheimsu'um's lair. Wounded and weary from the battles it took to claim the tome, they instead chose to run past the clerics and deliver it the dragon for protection. They succeeded in doing this and Yolheimsu'um bellowed for Galmin. The duergar approached for his punishment. Yolheimsu'um informed the Bellows former leader that he would still serve Tiamat, just not in his previous capacity. Hope glimmered in Galmin's eyes for a brief moment before Yolheimsu'um used his tail to flick the cleric into a nearby pool of lava. As Galmin screamed and burned, Yolheimsu'um commented how he would serve as cannon fodder against General Marshall's forces in the Nine Hells.
With that business out of the way, Yolheimsu'um sent two of the remaining cultists to fetch the adventurers rewards. They returned shortly afterwards and handed out the rewards as Yolheimsu'um explained their functions; a Belt of the Flame Dragon for K, Ring of Fire Starting for Bogo, Forgework Dragon Shield for Elycia, and Dragon Wing Bow for Jake. Their business now concluded, Yolheimsu'um dismissed the adventurers, eager to use the recovered tome to finish crafting his iron golem.

Magic Items
Ioun Stone, ???
Ioun Stone, ???
Ring of ???