Invoking the dark forces through magical incantations has been part of man's history from the start, for as long as entities incarnated into human form have been giving The Call to the Service-to-Self. The desire for revenge, to eliminate a rival, to steal from another, to increase personal power at the expense of others - all these desires are such a call.
The magical incantation or rituals such as pentagrams on the floor have nothing to do with The Call being given or answered, but practices that set the mood do. For instance, sacrifice or blood letting, particularly of an innocent or someone the participants are reluctant to sacrifice due to personal bonds, sets the mood. During such acts, the participants increasingly disconnect their empathy toward another, and concentrate on the self-satisfying goals that led them to the ritual. Are babies sacrificed, and by their mothers? Yes, but not as often as the public has been led to believe. Most often the human sacrificed is a peripheral member of the group, so that the cult leader can go on a power trip. He glorifies in his ability to make friends turn on one another, at his command. Such power trips become such a drug that more and more such rituals are performed and the outcome goes one of two ways.
Do Satanic Rituals result in demons appearing and humans striking a deal with the Devil? This is a parody on what in fact happens as it is not so cut and dried. The Service-to-Self entities answering The Call may appear to the band, but briefly. These demons may take any form, as they are above 3rd Density and thus can move between densities, appearing and disappearing at will. They may show themselves as they are or enhance their appearance to strike fear into the horrified humans and demand and get the subservience that all Service-to-Self entities seek, without abatement. The humans are indeed giving their souls away as they are joining the Service-to-Self orientation, where control and captivity are an everyday reality. Can the demons invoked deliver? No. All actions on Earth are due to humans, so rewards can only come from humans. As we are talking here of the Service-to-Self crowd, beneficence toward others is not likely. Moreover, the Service-to-Self are not known for truthfulness, and would lie in any manner to induce humans to follow a path that would benefit the entity answering The Call. Does the human want a shinny new car. He shall have it. Just kill the child. Of course, the car never arrives, but the human has often delivered his end of the bargain.
Satanic Ritual is a one way street. Humans go to hell, and get nothing for it.