So, there is a creature called nuckelavee which comes from Scottish mythology. People in Scotland used to tell stories about it a long time ago. It is a very scary creature because it is like two creatures combined into one.
The first creature part is a horse. The second creature part is like a really ugly, slimy giant. The nuckelavee has a giant head with one big, red eye in the middle of its forehead that glows in the dark. It also has a mouth that can open really wide with lots of sharp teeth.
When the nuckelavee walks around, it makes a loud, creepy sound like a horse but much, much louder. People who are unlucky enough to see it would often get very frightened because it is such a strange and fearsome-looking creature.
The nuckelavee doesn't like hanging around people too much, but it can be very dangerous if it feels like someone is getting too close. It can make people very sick just by breathing on them, and it is also said to cause diseases in crops and livestock.
In short, imagine a monster that looks like a giant, slimy horse with a face like a gargoyle that can make people sick just by breathing. That's what the nuckelavee is.