Azas

Imprisoned in The Purple Peach for an unknown period of time, entertaining itself with sadistic possession of any Halflings that entered the pub, the Loumara now identified as Azas was compelled to leave an IOU for The Ladies' Hiking Club after their interaction resulted in its freedom.
Little is known about its personality or desires, apart from its sadism and its desire for its IOU to be called in.

The IOU

The debt of Azas, bearing the sigil to the right, has proven to be a hot item, desired both by Mote and Torwall's Patron. The former traded it for Peaseblossom's services as emissary, and the latter demanded the ladies retrieve it from Mote and Thistle for his benefit, citing Beulah Garland's alleged use of his powers as pre-paid compensation.
It remains a mystery why this particular IOU, from a very old but comparatively low-ranking demon that had been incapacitated for decades at a minimum, is in such high demand. Peaseblossom made reference to Thistle having said it was their intention in buying it to "take it out of play", whatever that means.

The Genus Loumara

Vega Spritzer is familiar with Loumara generally. They are among the oldest of demons, said to be remnants of the dreams of dead gods that perished in the Abyss at the act of creation. They are incorporeal but highly skilled telekineticists. Loumara are not numerous but due to their lack of form they are among the most common to be found escaping into the Prime Material plane. Most are too weak to do more than smash an occasional plate or haunt a host's dreams, though the oldest and most powerful among them can possess weak minds (some nearly at will), communicate telepathically and manipulate objects with great speed and strength.
Loumara are truly incorporeal and not merely invisible. Many detection spells and workarounds such as Colour Spray are ineffective against them as they have no physical presence at all in this realm or any other.
Moreso than most demons, Loumara are bound by the old codes and, like their enemies the Fey, must repay favours performed and cannot enter residences unless they (or their host) are invited in. They are incapable of resisting the call of their true names and can be banished or summoned and bound to local habitation if that name is known and spoken in the context of a Banishment or Summon Greater Demon spell. (The use of the name both specifies the exact demon to be banished or summoned, and causes the demon to save against that spell at disadvantage.)
The sound of their names causes them psychic pain, though it is unclear if they can be annihilated by chanting as some demons can.
Most Loumara are nihilists. All are chaotic evil to the core, incapable of tolerating order or compassion.

Identification and Relationship with Naraoch

Through occult research in the library of Adalberto Veno, Vega Spritzer was able to determine Azas' true name, heritage and the fact that it was said to have been Naraoch's companion or "pet" in the events leading up to the Omnicide. Apparently when the Trilune Fellowship's fraternal order of mages captured the archlich half-in and half-out of the Green Dream and locked her into place with lanterns of the sort identified by The Ladies' Hiking Club in The "Lighthouse", Azas was at his mistress' side, meddling in the Fellowship's plans and seeking to possess St Astras as he struggled to exsanguinate Naraoch. St Astras "defeated" Azas -- the record is unclear as to how -- and it is similarly unclear as to what became of Azas after that point, as it focuses on the central and universally known events of Salvation Day.
In sum, it appears Azas had one epic fight with the greatest cleric in history, lost in a battle unimportant enough for the scribes to recount, and the next available fact is that it was practicing the Halfling Half-Gainer 1,354 years later.
Azas is now known to be the only Loumara born of the dreams of Azug, God of Chaos (though it is not Azug's only offspring by any stretch of the imagination). This may provide some context for the potency of Azas' psychic abilities, at least compared to other Loumara.

Confrontation in the Wandering City

On 21st Winterfell 866WA, the Ladies' Hiking Club invoked Azas, putting themselves in a Magic Circle and chanting its true name to lure it out. They devised a method of communication with the incorporeal entity, encouraging it to light torches: one for no, two for yes. They interrogated it at length, and at one point asked if the Fey had intended to keep its IOU to prevent it from doing harm to the world. In a fury, Azas responded with an inferno of "yes" that rattled the adventurers and prompted Peaseblossom to fall out of the circle.
After a few more questions, Fanny began to notice a slight clicking over her shoulder and looked over to Peaseblossom, who had become visible. With a passive, far-off look in her eyes, she was slowly and deliberately breaking her own fingers. Using Peaseblossom as a voice, Azas ridiculed the adventurers for believing anything it had to say and disclaiming its answers, making the entire interview unreliable. Peaseblossom then began to strain her own neck, choking to death.

In a fit of arrogance, Vega stepped out of the confines of the Circle to recover Peaseblossom, virtually challenging the Loumara to duel in her mind. She'd done it before with other Loumara quite successfully. Not so much this time. She was immediately overwhelmed and her body sprinted to the docks, leaving Peaseblossom sobbing in the dirt.
Thinking quickly, Beulah Mage Hand-ed the faerie dragon, still crying in pain and gasping for breath, back into the Circle. Beulah healed her quickly, relieving her pain but leaving her fingers sore and weak. Too afraid to venture out of the circle, the group stayed in place while Beulah shouted Azas' true name at the top of her lungs, attempting to break its concentration.
Just over a minute later, Vega came to her senses at the edge of a scaffold dock with her backpack dumped out and a length of rope in her hand.

Ambush at Commissioner's Hall

The following day, during the events of the Ambush at Commissioner's Hall, Azas possessed Violet Verihendrion Miller and led Fanny into a trap with a Sleep glyph, revealing itself with its voice as she fell unconscious. When the possession began is unknown. Once again Vega was the thorn in the demon's side, busting the door in within seconds and shaking Fanny awake. She confronted Azas, who said nothing but exhaled itself from Violet and left the premises.
It would be a funny coincidence if Azas tried to put Fanny to sleep for no reason while the rest of the group was fighting for their lives in the lobby. It is known that Azas can possess an entire pub full of people if necessary, but it seems a stretch to imagine that it was the party responsible for having set the ambush in motion a week or so prior.