Caligrosto

Caligrostos were a type of loumara (disembodied demonic spirits) that possessed bladed weapons to fulfill their bloodlust. The sadistic shades compelled their wielders to seek out new victims, which their current wielders could easily become.

Description
Caligrostos were inherently invisible—their natural state was an unseen, shapeless mass. While possessing a weapon, they couldn't be detected by spells such as see invisibility or locate creature, and spells like detect chaos or detect evil wouldn't unveil their nature as a demon, only their alignment. Under truesight, a weapon possessed by a caligrosto would appear to be seething with coils of lightning-flecked mist.

If a caligrosto-possessed weapon managed to injure anyone capable of using it, the caligrosto could take on a more distinct form. The caligrosto's incorporeal incarnation of its victim was both phantasmal and fiendish, a blurry, indistinct shade with features such as glowing red eyes, bat-like wings, and a forked tail. Regardless of the size of the victim, the caligrosto retained the same general mass.

Personality
Of the known loumara demons, caligrostos were thought to be the most sadistic, which, given the vile delights other loumara engaged in, implied cruelty so strong that even some demons might be taken aback by. Caligrostos were hateful spirits that from the moment of their conception had a deep-seated need for a blade's edge, living for little more than satisfying their primal, remorseless desire—the thrill of cutting and slicing flesh from bone. They could form attachments to particular weapons and would only abandon them in the direst of circumstances, after which they became obsessed with taking them back before enacting wrathful vengeance against the one that forced them to abandon it.

Caligrostos were also treacherous creatures, skilled liars with a penchant for deception. Though capable of being patient and in possession of a self-preservation instinct, their self-restraint was sometimes overpowered by the desire to betray.

Abilities
Caligrostos could sap the strength of others with their mere touch, allowing them to heal themselves if injured and obtain greater vigor even if already in peak condition.

Possession
Unlike other loumaras, caligrostos were limited to possessing unattended slashing weapons rather than living creatures. Any normal weapon could be possessed at will, but magic weapons naturally resisted possession, and if the loumara failed to enter it then it could never try again. Once they did possess a magic weapon however, they could enter and leave them as easily as any other, although they couldn't move or drain others whilst occupying a blade and were limited to observing the world and communicating telepathically.

Caligrostos could be forced out of their weapons using spells like banishment, dismissal, dispel chaos, and dispel evil, requiring them to overpower an enchanted weapon again to repossess it. Though caligrostos were incorporeal, the weapons they possessed remained solid, and destroying their tools also forced the spirits out and potentially left them stunned.

Caligrostos could infuse the enchanted weapons they inhabited with additional qualities alongside their existing powers. Ordinary caligrostos could infuse the keen quality, while more powerful ones could also add the wounding quality, and the most powerful of them could add the vorpal quality.

Shade
After a striking a valid target, a caligrosto could attempt to fly free from its wielder's grasp (requiring a strong force of will to keep them still) and create a fiendish shade that would receive and wield the weapon. They were uncannily skilled in the use of bladed weapons and were proficient with whatever weapon they were possessing, using their dexterity to wield it with lethal adeptness despite their lack of strength.

While theoretically able to permanently exist in such a way, a new phantom image would be created based on the next creature they struck that could wield their weapon. The phantom facsimile had keen insight into how best to attack the creature it was imitating, and had a bizarre link to the original. Caligrostos were immune to mundane weapons and resisted magical ones, but the displaced harm from being sliced unexpectedly affected the one they were copying instead.

Combat
Caligrosto-possessed weapons could be wielded like any other and, if the spirit so desired, they could refrain from making a fiendish shade of another creature. They often used their infusing powers to make the weapon they were haunting seem more appealing, thus increasing the likelihood it would be used in combat, and they sometimes even used telepathy to convince others that they were sentient weapons, typically with the intent of stealing another form.

After tasting flesh and blood, they attempted to escape their wielder's grasp so as to personally inflict bloodshed in phantom form, often trying to convince their "owner" that they were going to use a short but potent version of the dancing weapon quality so as to fly off without resistance. Once they were free, the caligrosto might first help their previous wielder defeat the current threat, or just immediately turn on them the second they escaped.

Society
Caligrostos preferred locations with as many potential victims and wielders as possible, favoring active places like forges, armories, and shops, to remote or abandoned locations. Ideally the weapon they possessed would be walked by every day rather than kept hidden, and they didn't need any treasures aside from their blade.

Despite their bloodthirsty behavior, powerful creatures, demons or otherwise, were sometimes able to get large groups of caligrostos to cooperate. Caligrosto legions would serve as guards and soldiers so long as there were regular opportunities to cut and stab, and they quickly adapted to the guaranteed supply of victims and security of working under a more powerful being.

Graz'zt's own "Razor Legion" was an example of caligrosto symbiosis. The cambion rangers that made up the legion, dangerous on their own, had their swords enhanced by caligrostos who made no attempt to fight their wielders. However, when the cambion wielding it fell in battle, the caligrosto could use its fiendish shade ability to take on the form of the last opponent and fight with even greater skill than the cambion, effectively granting Graz'zt two armies in one.

Creation
Caligrostos, like all loumaras, were spawned in the Dreaming Gulf, created from the dying dreams of a destroyed pantheon of gods. The caligrostos specifically were believed to have been the result of the nightmares of a god of craftmanship and healing.