"Devil" refers to the family of Celestial races originating from The Hells. Devils seek to subjugate the rest of existence, ensuring their own supremacy and powers by stripping away everyone else's. Much of devils' scheming involves securing claim to other's life energies, their souls, through the powers of law and order. They are one of the outer planar groups with the most interest in humanoids from The Material Plane, hoping to collect humanoid souls.

There are, broadly speaking, two classes of devils. The upper class of devils and the lower class. The upper class of devils have acquired great power, armies of lesser devils and oceans of souls contractually bound to serve them. They use their servants to grow their power, never fully satisfied with what they have, taking steep cuts of whatever their servants are able to acquire in their own dealings. They are the most powerful, dangerous, and ruthless of creatures.

The lower class of devils are, essentially, indentured laborers. They are bound to more powerful devils, who take steep cuts of their earnings, constantly slaving away to earn a pittance. This of course only drives them to work harder, believing that so long as they play the game and follow the rules, they will prosper. Few do, of course, and only the most conniving ever achieve their independence, and only ever on the backs of others. Some even believe themselves to be members of The Hells' upper class, when in fact they have merely been given just enough to keep them satisfied enough to stay in line.

Relations of other Races
Devils are less likely than demons to gut you where you stand, but that doesn't make them any safer. They have a way of luring the desperate or foolish into soul sacrificing contracts.

Contractually Bound

Devils are bound by nature to follow contracts, physically incapable of willingly breaking a contract. They can only take what another has agreed to give up, and only if they provide whatever payment was promised. They play the long game, providing services in the short term in exchange for hefty payments, often one's soul, to be made later down the line.

A devil can not initiate violence, but there are ways around this. A devil can attack in self-defense, should another invade their rightful territory, or use "necessary force" to reprimand one who has broken a contract with them.

See: The Devils' Law Code