Rise of Darkness
Devils are the epitome of the Lawful-Evil alignment. They are cruel and vicious, without a scrap of compassion. They are all self-serving and thoughtless. However, they obey a strick set of rules, though they are all seeking ways to exploit those rules. This was most proven when Asmodeus drafted the Pact Primeval, which stated that any soul having more sin in its heart than good could be used by he and his devils for energy to fight the demons. This was exploited by devil kind in that they began tempting mortals to commit sin and become Lawful-Evil so they could harvest them.
Devils exist for one major purpose: To win The Blood War. Most devils realize that they will never win and the best they can do is hold the Demons at bay. However, this requires energy, which has created their second purpose of harvesting Souls.
Unquestioning Defference to Authority: Rulers are obeyed because they are rulers.
Worship of Strength: Domination through physical prowess. Since the Pact Primeval prohibits devils from attacking one another except in certain circumstances: supiriors can always punish inferiors and a devil exceeding another by nine stations can discipline as well, this is generally proven in the Duelist’s Chasm.
Strict Rules: The Pact Primeval is their strict rules.
Intrusive Control: Authorities are always watching their subordinates and noting their activities.
Harsh Punishment: The slightest failure is met with extreme punishment. From torture, dismemberment, demotion, or death, ever failure is met with swift retribution.
Bureaucratic Precision: All transactions, no matter how meaningless, are recorded. Many layers have areas devoted just to the paperwork of promotions and demotions throughout the eons.
Exemptions for Rulers: Rules are meant for everyone but those who have earned or been given high authority. They deserve more freedom because they are rulers.
Expansionist Aims: Since their society is so superior to all others, devils seek to spread it to mortals wherever they can. This increases their soul intake, true, but it is because they believe so strongly that their society is the best is why they truly do it.
Any mortal society devils corrupt with show these same signs, just adapted for mortals.