"If the Eyes are the windows to the soul, then his soul was burning in Hell."
It was common belief in medieval times that goods and property could only be affected by the Fair Folk, the faeries, if it was acquired unlawfully or unfairly.
The gold hoops and rings that sailors wear are to throw into the sea if there is a storm. These are bribes to the sea gods to let them live through the storm.
Once a year, the king steps down from his throne, and lives as a peasant for one day, the next day is the anniversary of his coronation, and it is celebrated by a reenactment of the ceremony. This is doubly beneficial, firstly, because the people are able to have the grand parade that always precedes the ceremony. Secondly, because the heir to the throne is given a day on the job every year. Although, apparently, the thought has not yet come to one of the kingdoms enemies, the assassination of the king during the renewal coronation would be a moral, as well as a political blow to the kingdom.
A world where, instead of aging in years, the people age in knowledge. So, instead of dying once a general age was reached, they die once they achieve a certain amount of knowledge. A man could live forever if he never learned anything, or could die after reading a few choice books. Of course, the knowledge of the land would be regulated, like medical drugs.
What if a invisible person could see other invisible creatures? All you would need to do to check for nasties hiding around is turn invisible.
What if you send the players in a dungeon that was already raided? Maybe you could have traps that are already set off, or the corpses of monsters etc.
A place where an architect has built a temple/shrine to an evil god inside the walls of another building, a castle or another place of importance.
Sages and naturalists frown at the common name given to these strange creatures by the small folk, but sometimes the silliest nicknames for creatures, places and people persevere in the minds of many. “Purifiers”, “Pond Jellies”, “Breath-Stealers”, “Lung-Ticklers” and “River Butterflies” are much less commonly heard appellations for these life forms. Wet Faeries are basically (and simply) a species of fist-sized, fresh-water jellyfish. Several traits steer them toward the peculiar category however. Firstly, Wet Faeries are nearly invisible in the water, much like their marine cousins but even more so. One can swim in a river swarming with these critters and not even notice their presence. Secondly, they possess the unique ability to clean and purify whatever body of water they inhabit. They do this via some sort of biological filtration process, sucking in all toxins present in the water, and releasing it back in its purest form. Needless to say, they are both a blessing and a curse to whichever folk dwell beside the rivers and lakes Wet Faeries inhabit. On one hand, no purer water can be found anywhere than a Wet Faerie lake or pond, and yet, in “pure” water “life” tends in fact to die out, lacking the needed nutrients to prosper. Thirdly, their “sting” is (unfortunately) virulently poisonous to all mammalians. Wet Faeries are loathe to sting anyone or anything, using their barbed fronds as a last line of defense, but if stung, most swimmers will suffer respiratory arrest, and die within minutes, usually drowning before they can make it back to shore.
Alchemists, druids, and less savory characters have studied these creatures over the years, and have predictably found all the ways Wet Faeries could be exploited. Morbidly humorous, some bards find it, that the Poisoners and Assassins Guilds as well as the Healer’s Union, all prize these creatures. The assassins use the extracted venom in obvious fashion, while the priests and healers use the still-living jelly-fish to sterilize other poison potions and to cure those already poisoned on death’s door.
It is known that a certain Earl Von Trumble keeps his vast castle moat stocked with Wet Faeries, the waters so clear that every bone of every one of his past enemies can be clearly seen on the bottom, twenty two feet below.