Consider the idea of spontaneous genesis of life, as used to be belived. What strange kinds of life might arise from modern substances? What kind of vermin would a landfill produce, or an oil spill on the ocean?
Throw in a handful of random customs - like women or men of a certain level of society being required to wear a veil or a pendant of some type.
Magic is the lifeforce of all living creatures, and it is from it that all life is made - in areas with lots of undead, magic might actually be missing or weak, which puts a whole new spin on how dangerous the undead are. Even simple zombies can be troublesome if you're relying on mages and you hit a pocket of undead making a low-magic zone...
How about a dragon how cheerfully rules over a kingdom; his people all know him for what he is, and dragons are looked upon as wise and benevolent creatures. Dragonslayers from other kingdoms coming to free it from 'tyranny' are likely to get beaten to death by peasants with cast iron skillets.
A demon who isn't some hideous creature bent on consuming souls, bu is, in fact, a likable chap who enjoys having pleasant chats with people - trying to talk them into becoming his servants.
Someone needs the blood of a dragon, given willingly, to make a rare potion. Guess who gets hired to sweet-talk a dragon into giving up some highly powerful blood?
Faerie foods with unusual effects. Like faerie sausages that turn the eaters into wiener dogs, faerie wines that make the drinker whiny, etc. There's a table in Palladium Fantasy RPG which has a table of ideas.
The food that eats you back.
Creatures of nightmare, the thankfully rare Mesnoi have unique form and attributes. Only one Mesnoi at a time will ever be "encountered".
In appearance, a Mesnoi resembles a walnut-sized chunk of freshly-roasted red meat from some uncertain yet familiar, edible animal. The insidious creature camouflages itself quite appropriately whenever it can, by slowly making its way amidst feast tables and trays of roasted meats.
Once eaten by the unsuspecting, the Mesnoi sinks down to the stomach, reforming if chewed, and begins to lap up the gastric fluids, digestive juices, and bile that it craves, like a sponge.
The Mesnoi carrier will experience mild to severe stomach pains during this time.
After a few hours of this (this is the only time that the Mesnoi can be purged with magic, or other mundane means), the Mesnoi transforms into its true form inside its victim, that of a miniature, once more walnut-sized, pot-bellied, devil-horned, snake-tailed imp. This horrid little creature then begins to chew and eat its way out of the victim from the inside out with its tiny, razor-sharp teeth, like a rat forced to do so via torture.
The victim almost always dies a slow, agonizing death. That much is certain. The devilish imp then exits its victim and begins its seventy two hour existence of mischief and malevolence, until it once more turns back into a hunk of roasted meat with the movement capabilities of a snail.