If you want inspiration for your next horror monster, I seriously would suggest watching a nature documentary.
It can be good fun to marathon a bunch of horror movies to really connect with the genre and submerge yourself in it, I recently did so with the entirety of the Paranormal Activity movies. However, the danger there is you are only really seeing what has already been done, not ideal if you are wanting a fresh take.
Go on Netflix, on YouTube, whatever, there is no shortage of nature documentaries which are great inspiration. Ones that focus on the deadliest animal or on predators are especially for this purpose.
If you see something grisly and story worthy, then what do you do?
Generally, if you are writing horror, there are two options I would say, 1) apply those principles to a monster; or 2) make the creature prey on humans.
- Apply the principles to a monster
A wasp that paralyses its prey, drags it into a shallow grave and then lays eggs in the still living host? That’s nightmarish and great fodder for a horror story.
Using this method, you take what the animal does and apply it to your monster. Let’s say I had an idea for a monster terrorizing a small town but I wasn’t too sure on how I can make it different. I know it is a tall, vicious slab of muscle but apart from some generalities about how it looks, I am not sure how to make this a unique monster to keep my readers on the edge of their seat. I could use that idea, I make the monster abduct unfortunate victims, drag them off to its lair and then carry out the same process as the wasp.
There is the black widow spider that devours its prey, not hard to imagine that principal applied to a femme fatale style demon. Once she mates with a suitable target, she can tear their head clean off.
In these various examples, you already have an idea for a monster but aren’t too sure how to separate it from the crowd. Take an activity or tactic the animals use and apply it to that very monster and you will be left with a nightmarish result.
- Make the creature prey on humans
This is a bit simpler and can be very effective. Let’s say you have no idea what you want your next monster to be, total blank slate. We all get like that sometimes, when the ideas won’t flow.
Why not take one of the gruesome creatures you see in the documentary and make it able to prey on humans?
For example, in North Sea Nightmare, the monster is really a jellyfish big enough to devour people. To refer back to my previous example, why not use a monstrous human sized wasp that kidnaps people to be hosts for the brood.
If army ants stripping their prey to the bone in a matter of seconds creeps you out, then make the ants start devouring humans.
Find a creature that makes your skin crawl then make it focus on humans instead of what its natural prey is. The creature wouldn’t really be a threat to people? Then make it bigger or more lethal.
There are plenty of sources of inspiration for your next horror story, I would suggest a nature documentary.