balrog ~ glabrezu ~ hezrou ~ manes ~ maralith ~ nalfeshnee ~ succubus ~ vrock
Though demons have a wide range of powers, and many of them are very powerful, they are not free to wander from the Lower Planes [placeholder] simply because they have the means. Demons are very much under the control of powerful and malevolent gods, and as such are expected to serve those gods as commanded. However, this does not mean that demons are necessarily malevolent ~ they have tasks they must perform and some of these tasks do involve the torture of the dead, in specified ways ... but an ordinary demon might, if they free themselves from their yoke of service, choose a different path from malevolence.
PossessionAll demons have the power to possess creatures of every kind. For more detailed rules about this, see Demonic Possession.
Natural AbilitiesAll demons have specific abilities that are not spells. These abilities may be performed at will, which means that they require no more than 1 action point. Demons are, therefore, quite dangerous to face as enemies.
Demons 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. Additionally, demons can produce darkness at will, encircling themselves with a 20' radius of inky blackness, which can be dispelled only with dispel magic.
Demons are also able to gate in other demons, always of their own kind but sometimes greater or lesser demons as well. Demons will resort to this ability when they are pressed in combat ~ but only if their presence in a particular time and place is absolutely required, due to commands that have been given by the gods. Otherwise, the demon is far more likely to simply teleport to safety, as this is also among their abilities. Demons 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.
ImmunitiesAll demons are immune to normal weapons. To cause damage to a demon, the weapon must be made of magic. Take note, however, that if the demon is in possession of a creature's body, then the body itself can be killed by use of normal weapons. This body will have a set number of biological hit points (BU), but never hit points gained from levels, as the will driving the movement of the body is the demon's, that cannot benefit from the host's knowledge. Damage done to the body is not counted against the possessing demon.
If the host body is then killed, the demon will shuck it away, revealing itself for what it truly is. Often, up until it is revealed, a demon will hold back on revealing most of its powers, particularly teleport and overt magic; once it is exposed, however, the demon will likely unleash all the power it has.
Demons are have immunity to many elemental attacks, such as those that employ cold, electricity, fire or gas of any type.
MisconceptionsThrough the millennia, a great number of folk tales have arisen that suggest that demons 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 demons.
Demons have names, but having knowledge of these names grants no power over a demon. Demons 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 "demon's amulet" that maintains the demon's essence to ensure that it returns to the underworld after it has been killed on the Prime Material Plane ~ this just happens. Therefore, there is no special object that, if possessed, that makes a demon into a mindless slave.
For further information on the motivation of demons in the underworld, see Demon Culture and Origins.