The largest part of the population of Baator is made up, of course, of baatezu. These berks are real terrors, and their race is responsible for half the Blood War. Their fiendish minds and subtle cunning drive them to greater depths of evil than any tanar'ri could reach, and they seek to spread that evil (bounded, of course, by order) wherever possible.
The most common way baatezu extend their evil is by cutting a deal with some sod who doesn't know any better. The fiends have a distinct advantage in that far too many cutters think they can outsmart a baatezu. Even powerful mages and upright warriors have failed to fleece these fiends. Here's the chant: Baatezu have been at this dealmaking business for so long they recognize virtually all the loopholes.
The Baatezu will keep a deal with a berk, but they'll twist his words so much he might not recognize what he's said once the deal's made. Nevertheless, baatezu won't seize anything they don't think they've got the right to snatch. Because of their lawful nature, they have a backhanded sort of honor, but they'll try all manner of tricks to persuade themselves that what they're doing is the correct thing to do. If a body can convince a baatezu he's found a flaw in its logic, or that it left an escape clause in the deal, the fiend's got no choice but to let him go.
Obviously, the best way to make sure a berk doesn't get bobbed by a baatezu is by not making a deal in the first place. Each baatezu is brilliant in its own way, and they're all looking to extend their race's control over the multiverse. They're willing to do it one person at a time ... and that means that every encounter they have, they're looking for a way to gain from it.
Now, it shouldn't be assumed that just because every baatezu is expanding its race's base of power that each fiend doesn't have its own best interests in mind as well. Far from it. Baatezu are evil, and that means they look out for themselves before they do anything else. If they can get away with it, they'll turn stag for greater profit. However, the greatest profit baatezu can ge tis a promotion to the next rank in their hierarchy, and there's no chance they'll be promoted if their loyalty is anything less than true. Still, if there's only a fiend or two in the way of the next promotion, there's a good chance the "obstacles" will disappear.
The fiends of lower ranks (the larvae, lemures, nupperibos, spinagons, abishai, and barbazu) are typically of minimal intelligence. They are less able to plan for their future, and they're the most easily fooled of the baatezu. They're convinced their superiors are always watching them to make sure they're doing a good job and following the rules. Despite such imagined surveillance, these fiends are the ones most likely to break the rules. That is, they'll put someone in the dead-book the moment they discover they've been bobbed - if they think they can get away with it. As such, they're a lot like low-level tanar'ri and are given to wayward impulses. When promoted to the level of spinagon, abishai, or barbazu, these fiends often seize the advancement as an opportunity to do whatever they like. Promotion from these ranks is mostly a matter of chance or a result of casualties in the Blood War.
The midlevel baatezu (the oysluths, kocrachons, erinyes, and hamatulas) are both tougher and smarter than the lesser fiends, but they're still prone to an occasional mistake or two. However, promotion at this stage requires nearly flawless performance, and so their mistakes are very rare and not easily noticeable. When these fiends do make mistakes, chances are they'll be civilized about it - that is, they won't tear their antagonist to pieces. Of course, some fiends new to this level might interpret a contract as the opportunity to rend a bargainer limb from limb. After all, if it wasn't specifically stated ... Still, every fiend quickly learns that this sort of behaviour is strictly off-limits - especially when the reprimand comes from a pit fiend.
Above the midlevel baatezu are the cornugons, gelugons, and amnizu, all greater baatezu. These berks're extremely intelligent and powerful in combat. If they make a mistake it usually spells demotion, though if it's not too serious they might get away with severe punishment. Generally, however, gelugons and cornugons will keep theeir word and enforce those of other baatezu. Anything less would promote chaos, and thta's the last thing baatezu want. The amnizu aren't quite so amendable to order; they're convinced they're more qualified to rule than the pit fiends, and so they try to undermine pit fiend rule whenever they can. If their machinations fall through, however, they'll back down right away. Despite the amnizu's pretensions, the greater baatezu are highly united and loyal.
The mightiest among the baatezu ranks are the pit fiends, bloods who've worked their way up from the lowest baatezu ranks to take control of the fiend armies and chart the course of the entire race. Some of these cutters are so powerful they give minor powers the pause. What's more, there's eight pit fiends who're absolute terrors - they're the ones who command the armies in the Blood War.