Intent: To protect against SW incursions/effects.
Effect: Prevents breaches of the veil; i.e. negates some events (by extension it negates negative prosperity modifiers from such events), prevents SW beasties from being summoned into the province, blocks the EO's necromantic magic from sapping the life out of affected provinces. That sort of thing.
A secondary effect should be tied into the above; the current +1 prosp is probably not the best effect since it replicates Bless Land.
- supresses all prosperity modifiers caused by the Shadow or Shadow creatures for the duration of the spell.
- can cast Protection from Shadow (level 1 Battle Divine Spell that protects troops from shadowspawn) once per turn without having it prepared and without using the spell slot in any of the affected provinces, still need to pay the RP cost of the spell.
If we want the spell to be a focussed anti SW spell then the above 2 effects would make sense.
So the final spell effect could be:
The spell reduces the chances of Shadow World incursions, as determined by the GM. Negates any negative prosperity penalties caused by the Shadow World for the duration of the spell. Allows a divine spellcaster in an effected province (of the appropriate temple) capable of casting realm magic to cast the Protection from Shadow spell on units involved in a battle that are present at.
Which seems reasonable and focussed and a little more interesting than a flat +1 prosperity modifier.