A city is being plagued by a swarm of winged mice. The vermin can get anywhere, and they can easily avoid their normal predators by simply flying away from them.
A breed of small dog has the remarkable ability to talk, albeit in the repetitive manner of a parrot.
In one region of a forest, all of the trees are identical, down to the leaves and the twigs. If the PCs carve something into one of the trees, it could mystically propigate until it covered all of the trees, or could vanish since it was not carved into the one true tree.
Purple deer have begun to appear near the ruins of a fallen city, or other place of power. Hunting the deer is absurdly easy, as their coloration makes them easy to see. The heros prepare a feast from a freshly killed deer find out several hours later that the meat of the new purple deer is poisonous. This can range from cramps and vomiting to the truly sinister and lethal.
The Akhal-Teke is a real horse breed that develops a metallic golden coat. A more fantastic version could have a coat the color of pure gold, or silver making the horse appear to be made of the precious metal.
The Hierophant of Greenmarch is a lycanthrope. Rather than seeking a cure, or hiding his condition, he considers it a blessing from the Goddess of the moon, and requires that all of the Druids and loyal Rangers of Greenmarch to share in his gift.
A race of people identical in all respects to humans except for the fact that they lay eggs.
A demon in human shape that murders travellers, however, he can only travel a certain distance from his home.One the adventures have passed that point, he is no threat to them.
Magical Fiends: When a mage or wizard casts a spell and draws more energy than s/he needs Magical Fiends are drawn to that spot and they feed of the extra magic as long as they can. When someone's magic is being fed off of they can't cast spells as well and they feel weaker. The only way to remove a magicial fiend is for it to be drawn away by someone else's power or to go to the very spot you first cast the spell and kill them
Elven Light Horse - a lithe and small animal well suited to the forest home of the elves. It has semi-cloven hooves, a longer tail, like that common to unicorn illustrations, and always a snow white pelt. Lives inthe forest, able to stand on back legs to crop leaves from the lower branches of trees. Shy and easily frightened, but at peace when around elves.
Dwarven Mountain Pony - a small, and hardy animal well suited to living in the mountains and highlands. Able to subsist on grass and brush, with hard hooves, and nimble feet. The dwarves use them as pack animals, and to pull ore carts, and to drive bellows for their furnaces. Never ridden as dwarves like to keep both feet firmly on the ground. As stubborn and tough as the dwarves themselves. Also only about 12 hands tall (1 hand=4 inches)
The Orcish Mustang - a semi-wild horse tamed and domesticated by orcs to serve as their mounts. Large, strong bodied, and fearless as they live among orcs. On the other hand, bad tempered, with teeth problems, sometimes have hoof problems, and agressive. In lean times, or when an animal dies, the orcs suddenly have a dearth of meat, and hide to work with.
There is a certain kind of silver-coloured spider who's bite injects an addictive drug into the person that creates a sense of euphoria. Once bitten the PC has a 50% chance of being addicted to the spider's bite and will carry it around with him or her.Long term use leads to serious injury or death.At first the PC will just seem a bit slower or sleepier then normal.
Elves are not actually aloof. They are actually extremely family-based and insular, and often intermarry inside their families, making them uncomfortable around those not of their family. Therefore, they shield themselves behind pretended aloofness and coldness until they are comfortable in others' company.
Animals have parasites and diseases, so do plants, there are even bacteria that cann dissolve oil spills or plastic or what have you - why couldn't there be a disease living off magic - a magic item could be infected, losing power and speading the plague to other equipment it contacts, while a magic user would slowly lose his powers and contaminate all he works with or casts a spell at...
Arkths or Ravagers: These are large landbound crablike creatures about the size of Grizzly Bears. They live partially in the astreal plane. Their food is magic. They can sense it at huge distances. Since spells and such are hard to eat (being in motion) and magical places are the equivalent of a sea of krill to them, they are looking for magic stashed in concrete places. Their primary food source is magic items, alchemical potions, and enchantments. They do a pretty good job of mangling/ eating the physical aspect of said items in the process of chowing down. These things will be the bane of dungeons everywhere, as they will slowly eat away much of the treasure (and the magical traps... so it can be advantagous to follow these things). Note: They will attack people with highly magical natures (i.e. high magic powers). They will probably kill the person in the process of sucking out the power.
These goatlike animals, who have shaggy coats and layers of scales, are good retainers of water. They are close relatives of Suppoki. Their meat is considered a delicacy in many countries.
No desert tribesman leaves his settlement without a Rakda.
These creatures are desert animals that are much like huge, quadripedal sloths. They have a hide made of heavy scales to keep out gritting sand, and over that, a thick coat of fur.
During sandstorms, and when they sleep, Suppoki bed down in the sand, covering themselves up until they are miniature dunes.
Suppoki derive what sustenance they can from water sinks, dew, and underground insects.
Suppoki are often ridden by desert tribesmen. They are stubborn and slow, but are often the difference between life and death out on the sands.
Urbants-Creatures that move quickly around on their massive arms, and their "legs" dangle about from their torso, at about elbow length. They can move fairly quickly, but not as fast as an obese human, and can "jump" fairly high. Their "legs" are very powerful, and can kill with one blow. The bad thing is, Urbants cannot block attacks at their heads, which have relatively no neck, from the length of their legs being so short.
Khor are a monsterous and violent race. Within five years of being born, they grow to about half human size and are very, very inteligent. As they get older, they get larger... unfortunately they become less intelligent. After their adolecesence (about seven years), they grow to human size and are of a low human intelligence. As they age, they grow larger, slower, and stupider. Most of them end their lives 3 to 4 meters in height. Khor have been reported upto 10 meters tall, though those elder giant Khor do little but hit anything that disturbs them.
As they age they get larger, they don't seem to ever die of natural causes.
What to export or import....
Fabric: wool, linnen, silk...
Wood: raw-material, furniture
Metals: iron, gold, silver, copper...
Wine, beer, mead, spirits...
Animals: horses, sheep, swine, cows...
Coloring-powder (for fabric, ink...)
Raw-material to make fabric: unprocessed wool, linnen, silk...
Glass: Windows, figurines, glasses, raw-material...
Tea (not sure about my spelling here, but I mean the hot drink Englishmen drink instead of coffee!)