Spinagons, or spined devils, are the highest of the least baatezu. Given their status, they receive very little respect from the other baatezu castes. Still, most are at least aware of the potential that may be held by any given spinagon, as well as the fact that they all begun from that same status in their own ascent, however long ago that may have been.
This caste is the first thought by most baatezu as the first true baatezu, lemures being far too mindless to be worthy of the title and nupperibos being naught but a position of punishment for the unworthy. Their duties are most often those of messenger and scout, teaching them the ways of both Baator and the wider planes through practice. Spinagons are often thrown by their supervisors (sometimes literally) into situations seemingly beyond their capabilities purely to see how well they will handle them, as in many ways this stage is considered one of instruction and teaching. This caste is often also tasked with the inauspicious duty of shepherding the lemure and nupperibo hordes as no other caste wishes to handle the mind-numbing duties; with lemure hordes especially, it is often said to be akin to the planes' most thankless babysitting. A spinagon's small stature and eagerness to squeeze into dark, secluded areas also results in this caste often taking the role of spy, though most often purely for a fiend's personal goals. They are rarely allowed to participate directly in the Blood War but for cannon fodder as necessary, and even this is kept most often purely for those spinagons that show the least potential as higher baatezu.
Once they do achieve the honor of promotion, an honor bestowed only by a spinagon's direct supervisor, a member of this caste can ascend to anything from a black abishai (though this is reserved for the most hopeless) all the way up to an amnizu. Despite this rare potential — stories are still told of the pit fiend Greth advancing an especially loyal spinagon all the way up to hamatula status purely as a reward for service — the vast majority of spinagons are ascended into one of the abishai caste. Some even consider a greater promotion to be something of showing a spinagon their place, as the barbazu line of promotion is often seen as a necessary good, a dead-end progression.
Spinagons are most commonly found on the third through seventh layers of Baator, serving as messengers and lackies for the higher castes. In many ways, they act as the vermin they are often considered to be, swarming in small packs over the craggy peaks and secluded crevasses of these realms. As all baatezu, they have no real need for sustenance, but they enjoy the flavor of meat; intelligent especially, but they are weak enough that it is rare they get the opportunity to partake.
While spinagons are "hatched" from lemures, their next forms come about far more directly. First, a spinagon must have their spines ripped from their skin one at a time by the one assigning them their new position. Their body begins to weep molten ichor from the sores left behind, but it soon seals their wounds. Then, with no escape to be found, the spinagon's flames start to suffuse their entire body, scorching them from the inside. Over the course of a full three days, the spinagon's body is distorted as its spirit is stitched with its own spines to grant it its new true name, while meanwhile, the fires of Baator remake its internals and expand them into a body that's forced to twist into a new form simply to support it.
Not merely the least true baatezu caste but also the smallest, a spinagon stands barely three feet tall, with a slender build that gives very little in the way of intimidation or terror. Most appear as spine-covered, winged gargoyles with spiked tails and razor-taloned feet. Befitting this, their coloration is most often dark greys and blacks, deep browns, and rust- or blood-reds.
- Faces of Evil: the Fiends, pg.14
- Fiendish Codex II, pp.136-137
- Planescape Monstrous Compendium Appendix I, pg.29