Distinct from the demon, the origin of devils is very different. Devils are so-called because they were aligned with "the Devil" during the War in Heaven; the eponymous "Devil" is better named Satan or, in Zoroastrianism, Ahriman, and in the present is known in Europe either by the name of Dispater or Lucifer. He is known by many other names in different parts of the world. For simplicity, therefore, the word "devil" refers specifically to the fallen angels who were cast into Hell along with Lucifer, along with those supernatural creatures who were spawned by devils. The distinction is made by describing the former as "greater devils," or devils who existed at the time of the War, or "lesser devils," those devils spawned since that time. See Devilish Culture.
There are comparatively few types of devil. Those that are best known include the following, found on their own pages:
The 72 arch-devils that exist are of such power and unique characteristic that they are not included in the list above, though characteristics that apply to all devils also apply to them. Devils act almost entirely without supervision, being placed in specific roles within Hell or Hades and having particular tasks that they exist to perform. They are, most of them, quite malevolent; but this also includes a considerable amount of indifference, as they have casually watched over the systematic torture of the dead for millennia.
All devils have specific abilities that are not spells. These abilities may be performed at will, which means they require no more than 1 action point (AP). Devils are, therefore, quite dangerous to face as enemies.
Devils are able to see perfectly well in complete darkness or light. This ultravision is similar to the 2nd level illusionist spell of the same name, except that it is continuous.
Devils are able to employ various magical powers as well: suggestion, as the 3rd level illusionist spell; know intent, as the 2nd level cleric spell; cause fear, as the 3rd level illusionist spell and animate dead, as the 3rd level cleric spell. Devils can perform these spells at will, as noted above, so they do not need to be cast and discharged; both take place with the passing of 1 AP.
Devils are also able to summon other devils, always of their own kind but sometimes greater or lesser devils as well. Devils will resort to this ability when they are pressed in combat — but only if that presence is absolutely required. Devils will almost always prefer to give ground and return to hell rather than bring others forth to fight (though a greater devil may summon a lesser devil to take its place). Devils can teleport at will. They will make rich and continuous use of their teleport ability, moving from place to place in a combat more easily than moving even a single hex. They are known to attack, teleport, then use the remainder of their movement that round to attack again.
They have limits. They can only use one magical power per round, including darkness, teleport and gate. They can perform that one magical attack, however, and employ their physical attacks as well.
All devils are immune to normal weapons. To cause damage to a devil, the weapon must be made of magic. Devils also have immunity to many elemental attacks, such as those that employ cold, fire or gas of any type. Devils cannot be charmed, made to sleep or mentally affected in any way. They do not have minds that can be read with ESP and their intentions cannot be known. Even augury and divination can provide no information on their movements or designs.
Through the millennia, a great number of folk tales have arisen that suggest that devils can be controlled by various means that do not exist as limits on other monsters. These fabrications are designed to undermine very powerful monsters with tricks and shortcuts — and, in fact, are all completely false with regards to the actual nature of devils.
Devils have names, but having knowledge of these names grants no power over a devil. Devils are not repelled by the presence of holy symbols, relics or artifacts (given that they act in the service of many gods that also employ these symbols).
There is no such thing as a "devil's talisman" that can protect a person from a given devil or enable them to be commanded.