Though one of the lowest of the lesser baatezu, the erinyes (ih-RIN-ee-eez) holds an important dual role in diabolic culture: in Baator, they are the first to take the role of a true tactician in fighting the Blood War, while beyond their home plane, they are charged with applying their talents to gain true devotion from mortals.
Though none trustworthy enough to believe can say for certain, it is thought that the first erinyes were celestials dating back to the time of the Pact Primeval. Minions of Asmodeus, when he was dismissed from service and fell to Nessus, these celestials fell with him. Their wings were tainted, and their connection to the divine was severed. This, it is said, is why they differ from other baatezu in so many ways, and why they and their ascended forms alone (but for unique devils) hold the ability to bear young.
In baatezu culture, the erinyes is one of the first castes to be granted any actual respect by other baatezu for their abilities. Erinyes take their form in one of two paths. The first are granted the form as a reward for great accomplishments as an abishai, or the demonstration of high degrees of potential, while the second are given the form after "graduation" from the status of kocrachon, after they have learned as much as they can about the fine art of torture, and demonstrated that art in innumerous fashions. In both cases, however, the newly-promoted fiend is not given any great training, no newfound forms of education, for they are seen as far beyond that point. No, they are thrown straight to the wolves, sent to either the front lines of the Blood War or the communities of mortals beyond Baator in order to perform their task.
An erinyes's first assignment is determined largely from the nature seen in their abilities prior to their promotion. Those that show great skill in mortal interaction are first sent to exploit this ability for the sake of the baatezu (most promoted from kocrachon are given this initial assignment), and those that instead show great skill at combat or great tactical intuition are sent as lieutenants into the Blood War. However, all erinyes are expected to excel at both roles, and are given ample assignments in both regions; this is where many baatezu first begin to mature a breadth of ability, after all, and those that cannot excel in both areas, equally important as they are, are looked down upon by all.
In the Blood War, the erinyes is the lowest of the officers, directing the spinagon and barbazu soldiers according to the orders of their superiors, and often engaging in battle themselves. As the major front-line officers, erinyes have ample chance to practice their abilities in both tactics and strategies, often needing to lead situations unforeseen by the more distant castes and adapt to changes in the battlefield faster than orders can be communicated from further up the chain in order to ensure victory.
Their other role, however, is just as important; pulling mortals to the side of Baator in order to fuel the race through both spiritual energy and greater numbers. Unlike the falxugon, erinyes do not achieve this goal through promises of riches or power; instead, they ply mortals in such a way that they themselves will decide to come to the Hells. Whether through seduction, debate, coercion, or torture, an erinyes is meant to inspire not just promises, but true devotion.
Because of their differing methods, erinyes have a longstanding feud of sorts with the falxugon, each seeing their methods as far superior to the other; the falxugon tend to have a higher success rate with their contracts and bargains, while the loyalty of those swayed by an erinyes is of no compare to the parties of a falxugon. Erinyes have a similar feud with the succubus, though of far greater fervor of course — beyond the usual divisions of law and chaos, many erinyes see succubi as sex-obsessed fools that are far too quick to seek personal sustenance even when it is against the best interests of the tanar'ri as a whole. Ironically, with how often erinyes come into contact with succubi outside the bounds of the planes or the fields of the Blood War, especially in situations where they cannot simply kill one another due to the necessities of the mask, out of all castes they are those most likely to also hold some level of professional respect towards one another; they may think one another as blood enemies suffering from pure philosophical delusion, but their interactions in the field seem to temper this hate somewhat. As tempered as a fiend's hate can be, at least.
After decades of service, erinyes are given the opportunity to be promoted on just as any fiend. Most are promoted to the station of osyluth, but depending on their skill, can be promoted to hamatula, amnizu, cornugon, gelugon, or even pit fiend. Further, every decade those thousand that have had the most success on the Prime are promoted to the level of brachina and given the illustrious goal of bringing those whose faith and devotion is already promised to other beings (priests, cultists, and the like) into the fold.
Erinyes can be found throughout Baator, though the largest concentration can be found on Avernus amongst the armies of the Blood War. In addition, some secluded communities of erinyes dot this layer, where erinyes children are raised away from the wiles of other fiends that would wish to take them for their own purposes. Though all castes of baatezu can father young, only the erinyes, brachina, and noble baatezu can bear young, and as such they treasure their children greatly. Though fiendish love, even familial love, is a far crueler form than that experienced by most mortals, it is just as strong.
In these communities, erinyes children are taught the lessons and skills that most erinyes learn as they ascend the ranks of baatezu. As it takes but a century for an erinyes child to reach adulthood, most such "natural" erinyes are kept for much longer until they have the talents expected of them by other fiends. This is all under the approval of the higher echelons of baatezu society, as they have no wish for poor examples of baatezu to come into society. These communities are strictly sealed from all but erinyes and their kin, but for a single osyluth observer (always once an erinyes themselves) charged with keeping order as necessary. This kin always includes small numbers of alu-fiends, cambions, and tieflings, kept and taught no differently from a fully fiendish erinyes child.
The natural form of an erinyes is always female, much as the natural form of a falxugon is always male, though they do have the ability to shift their apparent gender. Physically, an erinyes will always resemble some humanoid race, though the vast majority appear most similar to humans or half-elves. The major distinction is in their broad, feathered wings, ranging in color from charcoal gray to pitch black.
But for gender, no erinyes has any natural ability to shift their form like their demonic equivalents. Some explore other methods of doing so if only to allow their work upon the Prime to proceed more efficiently, but others see such as crutches used by the likes of the succubi, and prefer to do their work wholly naturally. Given their continued resemblance to celestials, this often is not as ineffective as it may appear.
- Faces of Evil: The Fiends, pgs.14,20
- Fiendish Codex II: Tyrants of the Nine Hells, pgs.13,18,134-135
- Planescape MCI, pg.22