"you call … we come": The Cenobites.
Hellraiser
Basic Information
Invocation is the nearest "real world" equivalent to the summon magic usually found in RPGs.
It is generally neither as flexible nor as easy to use, but is frequently less of a challenge to the suspension of disbelief.
This style of working involves calling a supernatural entity into your workspace, usually under controlled conditions, for the purposes of bargaining with it for power, information or practical aid.
In an RPG this is generally high level magic, but in most magical traditions (and many a minatory legend) anyone who knows the right ritual (or something approximately right…) can get the target entity (or something similar) to pay them a visit. Doing so safely on the other hand usually requires extensive preparation and frequently mastery of binding magic and/or ward magic. This is what the traditional summoning pentacles, magic circles and what have you are meant for - although whether they provide a refuge for the wielder, a prison for the entity or merely a dangerous illusion of safety varies. These precautions may be part of invocation or may be a separate school - perhaps abjuration or simply ward magic. In some traditions, simply saying the name1 of an entity may be enough to attract its attention2 … how it then reacts will depend on the entity's character and the circumstances of the speaker - repeating the name may make a reaction more likely (and a certain number of repetitions may be required3), but may run the risk of causing annoyance.
There may also be a subschool of binding magic used to control and coerce invoked entities … or there may not be.
Getting rid of the invoked entity is another problem altogether.
Invocation may overlap with theurgy - particularly in shamanism or in practices like Kabbalah or angelomancy. Arguably this is also how someone becomes a witch - by invoking a lower power (whether as part of an act of worship or not) and bargaining for its patronage.
It may also be a prelude to something similar to summon magic by which the user bargains for assistance at some point in the future.
Sources
Game and Story Use
- Most systems handle this sort of thing pretty unevenly - it has the capacity for some deep RP, but on the other hand you need a decent mechanistic basis in case of problems.
- Eminently subvertable when writing a magic system - especially for players used to a more user friendly system of summon magic. Knowledge of The Charles Dexter Ward Principle is extremely helpful in this sort of case.
- Adjudicating when characters have thrown an specific name around enough to attract adverse attention may be interesting. Enough natter when preparing to summon may mean that the entity to be invoked turns up anyway.
- Also, for systems and settings where magic is less well understood, any given ritual may not summon what you expect it to summon. Equally, anything you find may not do what it says on the tin … but may still attract something. Likewise, rituals to ward or dismiss may not actually work. This may all be part of the hilarity of a magic system that is easily learned but very hard to master…
- Also note that even if you do learn the ritual to ward off the thing you're invoking and the one to get it to go away again afterwards, you have still advertised your existence to a supernatural being that probably didn't appreciate being disturbed…
- Many aspects of how this works will depend on the nature of supernatural entities in your setting - if, like medieval theologians, you considered a great many supernatural powers imminent to the real world and easily called across a very thin boundary then invoking them will almost certainly be easier than in the sort of RPG cosmology where the invoker must punch a hole through the dimensions.
Glendower: I can call spirits from the vasty deep.
Hotspur: Why, so can I, or so can any man; But will they come when you do call for them?
Glendower: Why, I can teach you, cousin, to command The Devil
Hotspur: And I can teach thee, coz, to shame the devil—By telling the truth. Tell truth and shame the devil.(from) HENRY THE FOURTH, PART 1 ACT 3, SCENE 1, 52-58 W. Shakespeare