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.
In the middle of the sky over the land of Dankij there is a door. The door is fixed in an upright position and appears to be fastened to the very sky itself. Worldwide rumors say it has been there since The Creation. What could be behind this door?