Naald

"How does a ghoul, a creature capable of coming back from hanging, impalement, suffocation, poisoning, electrocution, and even decapitation, commit suicide? Put simply, they can't. The primal aversion to fire is so great that even the most desperate would never consider self-immolation. Many resort to starving themselves. Instead of dying, they end up losing themselves to hunger: arguably worse, in a way. They become hollow, unthinking beasts, desiring nothing but to consume.
Then one day, the beast consumes enough to regain a level of sanity. Of course, it doesn't feel any better. If anything, it'll probably feel even guiltier at the damage that it's done. But as mentioned before, it has no real way to kill itself. So it just lays down, and waits to die. Hunger sets in, and the cycle continues.
Most ghouls are put down the first time they go hollow, often in the process of biting off more than they can chew: attacking particularly well-armed travelers or guarded settlements.
Naald, a ghoul of royal blood, found that nothing could best them, even in their delirious, half-starved state. Five times Naald fell into hunger, and five times Naald rose back to lucidity. Each time more cracked than before, until the imperfect reflection could no longer see itself well enough to find anything worth hating.
For the next seven hundred years, Naald's name would be the subject of frightened whispers throughout the south, spoken in the same hushed tones as the Scavenger or Amanojaku."

A ghoul adept at shapeshifting.
The general aesthetic of their appearance consists of a thin, hairless figure with bleached white skin, sleek horns, and red highlights. Often has sets of 'secondary' eyes around the main pair, reminiscent of a jumping spider.
Preyed on urban Eideli settlements for a long time. While arcahe could sniff them out, they could not traverse the more tightly packed structures common to Eideli cities. In some cities, the arcahe may reside in the local governor's manse, leaving a significant portion of the city outside of their influence unless currently in use (while in small villages, the village arcahe can sense basically the entire village). Soul lamps are also part of Naald's escape strategy: with their massive shapeshifting capacity, it's easy to change into a form with a similar surface Celestial imprint to a soul lamp, making it extremely hard for arcahe and such to track them.
Tended to wear the Stonewyrm's tear track-like tattoos, passing off their ghoul senses as the deity's blessing. Note that the underlying mechanism behind the two is actually the same, making this a pretty solid disguise. Eid based the stonewyrm's blessing on ghouls, after all. Naald actually once posed as a false coming of the Stonewyrm itself.
Post-Shattering, gained entry to the then-newly founded ghoul city. Was quickly exiled after murdering one ghoul, and brutally mauling another. Passes this off as a mutual thing- preferred being a big fish in a small pond to having every potential target being a ghoul.
After that, they found their way to Northport, where they ran a crime organization. Very hands-off: mostly just found the most competent 'right hand' possible, gave them full control after a display of force, then fucked off while occasionally checking in and directing members to their purposes, eating those who dissent in front of the others.

Shapeshifting

Ordinarily, ghouls can't shapeshift to the same degree that Naald does: 'neat' shapeshifting is based on self-image, and it's very hard to change this at will. Naald is unique in that they're enlightened several times over. Five times Naald has fallen into primal hunger, and five times they dragged themselves out of the madness. The other path to shapeshifting is extreme fleshcraft proficiency (see: Meraxes).
Forms include that of a rat, bird creature with several mothlike fatures, humanoid figure, and wolf-like figure with exaggerated jaws. Prefers not to take their 'mundane' form, hiding through stealth instead of disguise. A lot easier than one may initially expect, since they can shrink down to the size of a rat. A/N: remember the ghoul flesh-well effect. Squishing Naald while they are in rat form doesn't kill them so much as it causes flesh to spill out uncontrollably until they regain consciousness- generally around ~120-160lb of mass.
Naald has six forms: human, wolf, rat, humanoid, bird, and crawler-like monstrosity.
As a side note, these five additional forms correspond to suicide attempts. Ghouls can't just hang themselves etc. because of how much it takes to kill them, and the primal aversion to fire means they aren't exactly willing to do that either. Naald tried to kill themselves five times, faltering at the last moment and awakening as a feral beast.
The first attempt came from the first time they devoured a person, overcome by guilt. Their mother was still alive back then and nursed them to health. It's all gone downhill since.
Second after growing to hate their sibling and driving them away.