When it was first released one of DragonQuest's more unique aspects was its magic system. Multiple colleges with differing styles of magic in each made it very exciting and appealing. Being able to pick and choose what spells your Adept character would focus on was cool and meant that every Adept, even one from the same college, would be different. I really liked this and still do.
Like many other RPG systems DragonQuest includes rules for resisting the damage or other effects caused by magic spells. This is often called saving throws in other systems. Initially this post was going to be about damage from spells and why, for some spells, it could be resisted and others not. Particularly why spells that caused actual physical damage could be resisted. The longer I collected my thoughts about it the more obvious it became that the question I was really looking at was how does magic resistance work in DragonQuest.
[25.] Magic Resistance: All sentient beings have the capacity to resist magic directed against them. This ability is termed their Magic Resistance and is a function of their Willpower (WP), modified by their knowledge, the presence of counterspells, where the magic is performed, and how powerful it is (among other things).
From this I think it is safe to say that magic resistance is largely a mental effort (Willpower) to disrupt, dissipate or redirect the process or energies that are producing the spell effects. This also suggests that Passive Resistance is still an active process though possibly a reflexive one. This is supported by [31.1], "A character who is conscious and unstunned may make a Resistance Check to determine if he successfully avoids the effects of a spell." The unconscious or unaware character does not get to make a Resistance Check.
This explains why a spell which generates physical attacks such Earth Hammer (S-1) can still be passively resisted. The target isn't resisting the physical impact but is instead interrupting the magical energy that is sending the lump of stone at them causing it to miss or disrupting the magic that created it to begin with. This also explains why Adepts don't have to make Strike Chance rolls to hit the target for the majority of spells. Magic energies are directing the impact of the spell. Another Earth Magics spell, Diamond Javelins (S-17), supports that conclusion. Diamond Javelins can not be passively resisted and instead the Adept must make an attack roll to strike the target(s) much like a normal javelin. The spell conjures and launches the javelins through magic but once launched they are just normal missiles albeit ones of magically conjured stone thus no resistance.
So what about the Magic Aptitude (MA) characteristic?
[3.5] Magic Aptitude is a measure of a character's ability to harness and direct magical energies.
Why Willpower instead of Magic Aptitude? Seems clear that MA would be a natural for this. My belief is that it was mostly a game balance decision. All characters have WP and for non-Adepts it is usually quite a bit higher than MA. Using WP allows all characters, adept and non-Adept to have a chance at making a resistance check.
Why do Adepts have such poor Magic Resistance?
Non-adepts get to add 20% to their base Magic Resistance which is their Willpower. Adepts get their Willpower. There are other situational modifiers per [31.4] but they don't commonly apply. My rationale for why Adepts have such low resistance is that because they regularly channel magic energies they are more susceptible to those energies when the Adept is the target. That's kind of flimsy but its magic and its a game.
And now the problem...
One aspect of Magic Resistance that does bother me is Active Resistance. A non-Adept, with what is probably an MA of 5 and no training in controlling magic energies, is more able to disrupt the casting of another's spell than an Adept. There also is no range limit put on this by the rules and the one Actively Resisting doesn't need to be a target of the spell. Actively Resisting when you are the target can be justified easily enough. The action of casting a spell must incorporate intent about who the target is which establishes some kind of connection, however tenuous and temporary, between caster and target. It also means that any target actively resisting is, most likely, in range of the spell. This rationale also supports using WP for Passive Resistance.
Adepts on the other hand should probably use their MA instead of WP when Actively Resisting and would be able to disrupt the casting of a spell that wasn't targeting them but from no father than their MA in hexes. When an Adept is the target of the spell they are Actively Resisting they would also get to add in their WP.
In all cases, for both Adept and non-Adept, the resisting character won't know if they are or are not the target of the spell until the spell is cast. Their Magic Resistance and its effect on the casting of the spell will be determined at that time.
In my GMing and playing experience Active Resistance is used very rarely so it hasn't really been an issue. I do think that if someone were to do a revised/updated DragonQuest that Magic Resistance should be given a serious going over.