I've considered further, and come up with a new version of the ruleset that might be the best yet. This is only thanks to everyone who has pointed out problems so far - so thanks to all of you. I realised that most of the things I wanted PM to do could be grouped together under an umbrella of "force exerted by magic", which would also include the Rego protection in standard PM. So I decided to see if I could capture that in the ruleset, and therefore streamline it and make it more cohesive. This is what I've come up with:
Unless penetrated, magic resistance has three effects:
- Any spells or spell effects which target you, or something of which you are a part (e.g., a group or room) have no effect on you (exactly as in standard 5th ed. rules).
- Magic resistance reduces the force applied by any magic that reaches you to a negligible or non-existent amount. In this case, it does not dispel the magic, but it nullifies any coercive or harmful force exerted on you by the magic. Something akin to a magical armour that suffuses a magus.
- It makes you aware when something under the influence of an active magical effect comes within one inch you.
For the second point, “force applied” is defined as the act of gripping, controlling, inhibiting, harming or weakening the caster, or “breaking into” his mind, emotions or body. Any magical effect that does one of these things will have that aspect nullified. Examples:
- Magically-caused damage or fatigue will be nullified, including bonuses applied to damage caused by mundane means. The additional force created by the magical effect, in order to induce damage, is nullified. A sword covered in magical fire or a magically-sharpened edge will cause normal, mundane damage. A sword created by magic will stop on contact with the caster's body/clothes - its entire force nullified. A man with magically enhanced strength who punches you will only cause damage from his mundane strength - the extra force from magical enhancement will be nullified. The same man hitting you with a mundane sword won't cause extra damage, because the additional magical force of propelling the axe will be nullified. If the same man pushed a boulder from a cliff onto your head, you would take full damage from the boulder, because none of the force that reached you was magical in nature - it was the natural force from falling. (In game terms, this is easy to adjudicate - has the man's Strength made a difference to the amount of damage suffered (not whether it was suffered)? If the answer if yes, his mundane Strength should be used unless the effect penetrates PM - see below, this italicised part needs more thought).
- Anything that is actively magically-controlled or propelled (Rego) will be physically blocked from reaching you, stopping or being diverted about an inch from your body – the force of propulsion is nullified.
- Any magically-controlled or created entity (unless it is now mundane through a ritual) will be able to exert no force on you, becoming weak when it gets next to you. So, magically-controlled vines that attempt to wrap around you will quickly fall away; magical water will exert no pressure on your body, or be able to enter your body or restrict your breathing in any way; and a magical wind cannot knock you over or unbalance you.
So the idea of magic resistance negating the force applied seems to suddenly link a whole load of apparently different protections together under one guiding concept, while avoiding pink dot and boulder.
Please go ahead attack this with the same vigour as the previous iteration, so I can continue to assess it and identify problems. Right now, to me, this seems quite clear, concise, fairly easy to adjudicate, quite comprehensive in the protection it offers, and avoids the pink dot and boulder problem. That seems too good to be true so I'm probably wrong on at least one of those - see if you can discover which and let me know!
EDIT: The italicised bit about the enhanced strength needs some thought and clarification, but mainly because I'm not sure how this works in the standard PM rules - if a man with enhanced strength throws a mundane rock at a magus, what happens? And if the same man hits him with a mundane sword?