“ 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.”
“ Nearly every primitive culture has had rituals and celebrations to guarantee the proper passage of the seasons and to ensure the fertility of crops and animals. Oversight of these ceremonies was generally the provenance of local kings or priests.
Suppose that the adventurers dispatch one of these fellows. The local peasants may become hysterical, fearing famine and death will stalk the land. Alternatively, they may want one of the new heroes to become king. For a while, this can be a good thing, but the first time that the crops fail, the superstitious locals will want to sacrifice their new leader.”
“ On a planet with an ammonia atmosphere, that is inhabited by intelligent aliens, the police carry oxygen spray, that has the same effect on that planet that pepper spray does here.”
