They're out there.
Most people think the Vetter don't exist, that they are from old folk tales from a time when people needed the supernatural to explain natural phenomenons. They think they're safe in their logical modern world with their technology. Cushioned by the safety of disbelief, people forgot to pay heed to the powers of nature, the old rituals of respect lost in the technological revolution of modern times.
Until now the few people who still follow the old ways have managed to keep the Vetter content, showing respect through nearly forgotten rituals from the past. These people are a dying breed, getting fewer by every year that's passing by. Soon they won't be enough to keep the Vetter at bay.
And when they start emerging from their underground homes who knows what will happen to us humans
Don't worry, though. It's Just Folk Tales after all.
Or is it?