A player in my PBeM game wants to cast Bewilder out-of-combat on an inspector who is looking over their wagon for smuggled goods. He's of course hoping that the Perplexed condition is going to reduce the inspector's Observation check and hopefully miss some of their items.

How would you adjudicate subtle spellcasting? I want to be very careful here, because if it ends up being too easy, I'll have set a precedent that I'll later regret. If I make it too hard, I deny the character a chance to do cool things. My first inclination is something like:

To cast undetected: Stealth vs Observation, +1 Misfortune Die per spell rank (or Challenge Die?)

In addition, the spellcasting check itself gains +1 Challenge Die.

I'm somewhat worried about power abuse, so I would likely also restrict this only to spells that "feel" like they could be stealthily case. Magic Dart, no - Bewilder, yes. Or would you not allow subtle casting at all?

Thanks!

How about ignoring Stealth and just relying on the boons of the spellcasting roll? Decide how many boons he needs to be undetected. If he succeeds but doesn't get enough boons, he cast the spell, but the inspector or someone else nearby notices it. If he fails but gets enough boons, nothing happens but nobody's the wiser.

Perhaps the number of boons required could depend on the Stealth vs Observation ratio, even.

Well personally I would use:

No vocalisation: +1 challenge

No gestures: +2 misfortune

This would apply to bound and gagged casters too. It would than be an Observation test to spot the caster was 'up-to-something'.

As Grey Order magic is all about subtlety you might want to have Stealthy/Subtle channeling/casting easier for them.

As most college wizards make their status obvious by their robes and bing any supernatural event occuring within three or four miles will be attributed to them anyway.

Maybe even a Guile check instead of Stealth.