Wow. This might just be the hardest prompt so far. An urban myth?! A new legend? A local nightmare?
Maybe it would be a fun legend. After all, does it have to be scary or menacing? ‘Legend has it, that at every Full Moon, we all briefly become our inner furry’. Cue gluing feathers or fur onto people in the dead of night, so when they wake up, they wonder if it’s true. Mind you, there’d be a few questions around the breaking and entering…
It would be (I think) quite easy to start a rumour about a big cat, or some fearsome animal, prowling the streets in the dead of night. One need to point only to shadowy forms, and behave in an appropriately troubled manner, to persuade others that something is lurking in the bushes. If I was feeling particularly ambitious, I could sneak around in my meerkat costume in the middle of the night, creating a bit of mischief. As I’m the UK, I’m unlikely to get shot (though getting arrested is a possibility).
I really don’t know. Do I convince people of a big cat, roaming the land? It’s probably the easiest of all the myths to create, but it feels lazy. However, I am not feeling especially creative this morning, so I might have to park this prompt, and maybe revisit it.