They are not native to the world they are in, they visit it through magical links. Their own world, although little is known of it, is thought to be as every bit as complicated as our own. They look almost helpless with their gauzy wings like those of insects, and their average size being two inches.
They have a very dangerous bite however, that can (not permantly though) paralyse a human within half a minite, and they are a lot stronger then they seem (maybe through magic?) Twelve or more can carry away a human, as for human impliments, it just takes from one to four to carry them away. If fighting a human, they try and stay out of reach of weapons and hands, and dart in and bite. Or they ambush them.
Those who humans see are the bravest and most enterprising ones as only they will leave their home-world. And their favourite food (only eaten at their greatest festivals) is human flesh.