Official Answers from Chaosium
This covers the first part of Chapter 2, pages 8-9.
For the Rune Magic Spells, see Rune Magic Spells Q&A
|What is Rune Magic?||8|
|How Does Rune Magic Appear, Sound, and Feel?||8|
|Common Rune Magic table||8|
|Characteristics of Rune Spells||8-9|
|Stackable Rune Magic||9|
|One-use Rune Spells||9|
|Devising New Rune Spells||9|
|Rune Magic Spells Q&A||10-104|
Stackable Rune Magic (page 9)
I was GMing a game in which the players were preparing for spirit combat with a huge entity. They proposed to stack several castings (from different characters) of Spirit Block on the one doing the fighting. I ruled that it is not possible, since the definition of stackable in TRBOM says “The caster can add additional Rune points to the spell if the spell is described as ‘stackable.’ “, which implies that only the caster can stack additional points. Is that correct ?
Yes only the caster can stack additional points. The others would be casting separate versions of the spell, with only the largest being effective. A GM may also reasonably rule that each casting of the same spell displaces a previous one, leaving only the last one active.
There are are circumstances where you can stack, but it’s usually only with POW, see Combining Rune points in the Q&A.
Do magic points spent increasing a spell’s efficacy (e.g. points spent as part of Sword Trance or Heal Wound) increase the strike rank, or just those added to make the rune spell harder to dispel?
All magic points, unless the spell states otherwise.
Stacking spells from different sources – Shield and Protection, for instance. A character with Protection 3 running from his allied spirit may receive a Shield 2 from the Ernaldan supporter. Do these spells stack?
Yes as the description of Shield states:
The effects of this spell are cumulative with both Protection (page 118) or Countermagic.RBM page 78.
Would a Shield 1 by the character himself (boosted with 3 MP) add to the Ernaldan’s two points, or would that spell only stack with the Protection?
A Shield 1 cast by the adventurer on themself while a Shield 2 has already been cast on them would have no effect (not work). As a GM you can decide if the spell just doesn’t work or they waste their Rune point.
Would it not get cast to any effect at all?
Yes. No effect. It just doesn’t work.
Or would it exist but just not stack? That is, if the Shield 2 gets dispelled, is there still a previously non-stacking Shield 1 “underneath” it that now has an effect?
As a GM, you can have that happen if you so choose. The former will save adventurers’ Rune points.