When anyone attempts to attack the recipient(s) of this spell with the particular weapon, the attacker suffers a penalty equal to the casting level of the Spell. For example, casting at level 1 costs 2 Mana Points, and gives attackers a penalty of 1d20. Level 2 would be double cost (4 points) but would give a 2d20 penalty.
The 'weapon' is specific weapon such as 'Greatsword' not a category like daggers. (Some rare powerful varieties will protect against categories; add 1 point to difficulty.)
This spell is only extendable if the caster is the target; but the Duration may be doubled as normal with additional levels. Area may also be doubled, but all targets must be touched by the caster when the spell is cast.