Seems a might powerful for the relatively low charge cost- I'd bump it up to two significant charges, myself, or one and drop the +10% magic.

The reason I made it a minor ritual is that the ritual can work and yet the caster ends up getting nothing. There is a chance that instead of getting buff you get beaten. Besides if you miss the chance to use it you have to wait until next season.
The actual number of minor charges only matters for adepts. I can see how still having enough charges to use one's blast makes the ritual more effective since you aren't taking that big of a risk. Instead of making it significant I'd say you have to fight the person using Struggle. No blasts.
As for the bonus to magick I didn't mean magick while in sunlight but magick that involves the sun. If someone knew Greater Blessing of the Sun or Cause Eclipse the bonus would apply to those rituals.
Still I agree that 5 body points for a minor ritual isn't too shabby. You can regulate how easy it is by the strength of the challenger. I'd personally say the challenger is evenly matched except that Struggle is their Obsession skill. I guess I should have made it clearer that the ritual just summons the challenger whose defeat causes the empowerment.

Wait... there's a paradox.. nah I'm afraid it's just an ordinary contradiction here.

They must stand still all day, yet they must also fight and defeat a challenger.

Doesn't say how they must fight them.

Technically, a 'fight' could be a verbal sparring, or a game of chess.

Russian roulette, maybe?