There are several ways to used Spirit Assisted Magic in GURPS.
The example given in Thaumatology is a generalization of Demonic Contracts and Black Magic.
Concept[]
A spirit (or occasionally a group of spirits) casts spells through the wizard who may or may not need to provide their own fatigue to power the spell.
Possible Benefits[]
- Easy Spell Access: A spirit "teaches" a wizard how to ask the spirit to cast the spell claiming it is a easier version of the spell where Hard spells are learned Easy, and Very Hard ones as Average.
- Completely Free Spells: The spirit provides as much of the energy cost as is possible regardless of the wizard wishes on the matter.
- Non-Mage Occultist Casters: Magic is actually coming from the spirit involved eliminating the need for magery in areas not very high mana.
Possible Downsides[]
- Pact like requirements to utilize the spirit's power.
- Failed Castings: Spells operate as if the wizard was in a very high mana so normal failures are critical ones and critical failures are spectacular disasters.
- Spiritual Distortion: A skill penalty to any spell cast without spiritual assistance. Even with multiple spirits there is only one Spiritual Distortion tally. The wizard can get caught up in rivalries between the spirits especially if the wizard are seen to favor one group over the other. Once a wizard hits 10 levels of Spiritual Distortion the wizard develops an addition to using those spirits and their advantages and disadvantages will change to be more in keeping with their goals.
- Soul-Cleansing: The way to remove Spiritual Distortion. The wizard attempting this must forgo all spells casting for a certain amount of time. Base time is (20 - Will) days per level of Spiritual Distortion to be removed, minimum one day per level.
Note[]
While on the surface Roma Arcana would seem to have Spirit Assisted Magic spirits actually are a stand in for mana and magic generally works normally (casting time is longer though).
References[]
- GURPS Thaumatology 90-94