Demons

Demons are the chaotic, evil dwellers of the Nether Realms, or Abyss, who love to torture and butcher weaker beings and are kept in line only by the ruthless Hierarchy of Demons under Mephistopheles. A summoner must be harsh with them: the least hesitation looks like weakness, and the demon will then try to twist the sense of his orders. They flinch at first from holy symbols and artifacts of Divine Magic, and lesser and greater demons must attack devils on sight or answer to Mephistopheles. Mephistopheles, said to be chaos itself and known down the ages as Abadon, Typhon and Baelzebub, hates so completely that he would wreck his own dark realm to drag the rest of creation down with it.

A flawed Circle of Protection or Thaumaturgic Triangle leaves an evil summoned being free to enslave or slay its summoner (a demon may even take over his body), and one that slips out of a pact may come back later for revenge. Ordering it to do anything beyond the service its kind owes breaks the pact at once. Demons are swayed by offered riches and always accept a human sacrifice, and a devil offered as sacrifice pleases them too.