Cacodemon

This spell summons a demon or other fiend (such as a devil) from the lower planes of existence into the material planes. In order to cast the spell, the caster must know the fiend’s true name, but such information is often contained in forbidden tomes of lost lore. The spell cannot summon the lesser sorts of demons that have no personal names, nor is it powerful enough to summon members of the demonic or diabolical nobility. The spell provides no protection whatsoever against the wrath of the summoned creature—and make no mistake, the summoned creature will be extremely resentful of the caster’s temerity.

In general, this spell is cast only with multiple protections against the summoned fiend, such as a pentacle to contain the demon and a magic circle to protect the magic user. The exact nature of any discussions or negotiations with creatures of the nether planes is, of course, a matter to be handled in the course of the game, with the GM deciding what the fiend is thinking and how it acts.

It is treacherous in the extreme to deal with demons, for they are intelligent and ruthless. They are not, however, unreliable; since the caster knows the fiend’s true name, it is compelled to abide by any agreements it might make, although it might be able to twist the spirit of the agreement while still abiding to the letter of it.

Certain spells (spirit-rack or trap the soul, for example) can be (and often are) used to strengthen the magic user’s hand in any negotiations with a demon.