Chekov's Spell -- This spell has a two-fold effect. The first is to make the target item almost-unnoticeable to anyone not specifically looking for it. The second is that someone who has seen the item will remember it when they encounter a situation that would be perfectly solved by use of said item.
A world where there is a finite amount of magic present in the world, and it's almost used up. With the winds of magic being weak and unstable, how will nations built on the heavy use of magic survive?