Devil's Spite
Devils are no strangers to infighting. As a matter of fact, the best way to dispose of a fiend is to wield the hatred of another as a weapon.
A Devil's Spite is an abstract weapon formed when a devil formally antagonises one of its kind. It is a formless tool, a creation of the mind hooked to the belt of its maker, displayed more for demonstration purposes than intentional use. If there is one thing a devil dislikes more than order and staleness, it is putting itself in danger. Furthermore, they know better than to put their own lives on the line to take out their rivals. Humans make for marvellous intermediaries.
Yours for the taking
Occasionally, a devil will approach a survivor under the guise of a fellow Looter, rarely bearing their real face. It would pretend to come looking for a trade, asking for a service or help, and promise as payment the embodiment of their spite. The unsuspecting contractor who accepts becomes bound to exact the devil's will. For a short time, they become heroes of their people, stronger, faster and deadlier,until they finally come across their fateful encounter.
Should they vanquish their foe, the spite vanishes from their grasp, leaving them as powerless as they always have been without external help. In the event of a defeat, the token of hatred is taken by its target, absorbed to strengthen its abilities, resulting in a complete loss for both the survivors and the spiteful devil.
Over your dead body
While extremely rare, humans can sometimes fell devils by themselves. In situations like these, many arms can be collected at once for the one who knows where to look. As possession of these trinkets is not the result of a devilish contract, they can be traded and manipulated without having their destiny altered, though that does not mean they are harmless.
Knowledge about Devil's Spites is scarce and they are easy to miss. Some people can carry several of them unknowingly, while others dismiss them as lies intended to make survivors willing to put their trust into a devil extending its hand.
Many-edged sword
A Devil's Spite is no ordinary weapon. It may not even be a material object. A promise unheld, a lingering thought, the bitter aftertaste of dust can all be manifestations of contempt. However, the ones aimed to be wielded by humans are oftentimes tools, tokens or charms held close to the heart, as they found it easier to draw power from a familiar instrument.
Using such a weapon is not without consequence. Each strike infused with the evil's might has a high cost for its user. Sanity, identity, senses, memories... all are eroded in time, until only a mindless blade-swinging husk remains. Heroes die young, those aided by a devil even more so. Despite that and even after realising that they are going to lose themselves eventually, very few humans abandon the Spite to live a few more years. Either drunk on their newfound might or driven by self-sacrifice, they prefer a short life of going toe to toe with their persecutors than a longer one cowering in fear.
Stabilising the tool
A few scholars aware of the usefulness and risks of a Devil's Spite have gathered together in order to find a way to alleviate the drawbacks of its use. They made very little progress until now, their best lead being Marcus, the wanderer, a man who's repeatedly claimed not to be an ascended and has a large collection of esoteric weapons that seem to have no adverse effect on him. Unfortunately, the wanderer is very elusive and never lets someone catch him if he is unwilling.
Oh this is so spooky! I wouldn't want to run into a devil using this, like, ever D: