An old, misanthropic and paranoid man feels his time is coming. There are sons to leave his fortune to, but they are not worth it, not a dime do they deserve! And he doesn't really trust anyone else. And so he has made a decision: as a part of his last will, his henchmen are instructed to burn and destroy all his holdings, buildings as harvest. The lands shall be auctioned off, the proceeds used to pay the servants. Nothing shall stay behind. Nothing.
Depending on the status of the grumpy old man, this weird occurrence may be only a family drama, or it may end up bringing an entire region into chaos. Or the son(s) have found what should happen, and want to prevent it before their sick father dies.
Adventurers are to capture an unknown monster for examination (for a sage or wizard) but they are themselves captured by the monsters, and researched.
Temple of some malign being invites you warmly and offers help (curing,needed spell etc) for some minor sacrifice . Sacrifices must be everytime bigger to work - up to living inteligent creatures. Maybe you pay some other price,too...
The adventure can take place in a slightly shifted reality, where everybody has a totem (an animal guardian). The totem should be chosen randomly and not by the player, it is ok if "Gorflin the Large," a gigantic and aggressive barbarian, has a mouse for a totem.
These totems will assist the characters in small way. It is up to the characters to determine how to get the assistance; the animals won't solve mysteries for the characters only supply the clues. The character may even have a dream where his or her totem actually speaks to them and reveals some sort of clue.
There is a person who has a well-known reputation, probably involving something illegal. But this person is either very clever and crafty, or really like his or her privacy, for no one knows who this person actually is. As an added twist, perhaps this person is of an age that would noramlly be wildly inappropriate (say, a child is a much-feared bandit) or maybe not the expected gender or even race.