Events in an Ars game yesterday had me thinking of ways to find out if an opponent has MR. Trying to “kill something with fire” will always tell you but it has drawbacks. What about a light “touch” spell?
A few of the expansion books added “forceless casting” which allows a spell to work but have zero penetration, in a manner similar to most magical devices. Useful for casting where you think a Hermetic wizard might be within your targeted area, but the wizard casting the spell also needs to remember to use it. Oft times having a little extra force behind a spell is useful.
Within the game scenario the potential target is probably without MR but might be a special creature type. It is very unlikely to be an Order of Hermes magus. In this case I may not want my character to cast forcelessly, I want the effect to penetrate any MR it might have, so I get a sense that it either has none or not much. If the spell is low level enough it could be cast a few times to test both those scenarios.
My quick requirements for the spell are: target at Range: Sight, very hard for observers to notice, and especially easy to cast. The lower the spell effect the better.
Any spell Form guideline of level 1 is useful as it can be extended to suit, so I picked Muto Imagonem. Imagonem is very handy as it can affect any substance without an additional casting requisite. So the spell below can be cast on objects, animals, humans, or almost anything really.
Subtlety Walk Between Sunshine and Shade
Muto Imagonem 4, R: Sight, D: Momentary, T: Individual
The hue of the target’s image subtly shifts, to either slightly lighter or duller in a manner similar to cloud passing over an object on a sunny day, or the reverse. The caster may choose which effect at cast time.
(Base 1, +3 Sight)
The effect is simple and subtle. Other observers may be able to notice the effect, although it will be exceedingly difficult unless warned in advance. A creature with magical resistance will always “feel” the effect if they successfully repel it, but with this spell others won’t really notice it.
More custom spells can be found in the New Spells for Ars Magica page.