Let me see if I can help a little.
> First, my assumption. I'm assuming that if Korolvanth was just using the Air rune affinity and not the Thunderer Feat, there would be no problem: he'd be able to continue attacking with the Air rune affinity (doubtless subject to broad ability penalties, etc), and the Lunars would attack back with the Mood Madness power: for non-Feat abilities there is no sense of needing an "appropriate defense" - that's what the Mismatched Goals rules cover.
That's correct.
> So, the Thunderer Feat doesn't cover defense against the Lunar Moon Madness power, rules the GM. I'm curious as to why, and what else it might not cover defense against. By the Feat description, it uses crashing great sounds, gales, fiery winds, etc, striking armies senseless and making lesser beings flee. So presumably if your opponent fights back with physical weapons, particularly bows, etc, you're fine. But what about magic?
Depends on the magic - Glorantha does not make quite the distinction between magic/not-magic that many fantasy settings do. So an army that attacks with angry killing spirits, a foe that called upon spirits (lesser beings to Orlanth) to attack the devotee, or an enemy heroforming some other god could well be fair game for the Thunderer Feat. But Moon Madness is something entirely different - it exposes the Thunderer to the Red Moon's paradoxical powers and drives him nuts. That is outside of the feat's description. Similarly, if the foe sent a beautiful seductress to make him forget the battle he could not use the feat to overcome her beauty.
> As this applies to the logic of all Feat use, I'd like to understand it. What do you think is behind the GM's decision?
Look at each feat as a mini-story. Things within the scope of that story are within the scope of that feat. So with the Thunderer feat, hostile foes who confront the Thunderer are going to get smashed, but a beautiful seductress is likely outside the scope of the story. Or a Lunar philosopher whose insight is madness.
Does that help at all?
Jeff
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