From skimming over the wikipedia entry, a thought comes to mind: Sawney Bean's offspring. According to the entry, there where quite a lot of them, which could be his actual offspring, or it could be 1 entity that is able to spawn more of itself. Bonus if it looks like a creepy kid (like Village of the Damned).
For puzzles, I always liked the everchanging maze, common in pc adventure games. A headache and a half to plan, but your players are going to crack their skulls over it, too. The idea is, that it is not only important where you are going, it is also important where you are coming from. So if you enter an intersection from the north and leave to the south, you would enter the same intersection from the east. If you go south again, you are at a dead end, but if you leave the dead end, you appear at a 3 way intersection. And so forth. It is kind of tricky to map out all the ways, but it is doable.
