It could be the main character themselves. Sometimes, in a psychological thriller, the character discovers that they are the source of all the problems, and in a way, they are the monster.
Well, it could be a symbol of fear or the final challenge in the story. Maybe it represents the unknown that the characters have been dreading all along.
The significance could be to create suspense. It makes the reader curious about what the monster actually is, whether it's a literal monster or a metaphor for something like a big problem or a character's inner fear.
I'm not sure as you haven't told me the specific story. But it could be various actors or characters depending on the nature of the story. For example, if it's a horror story, it might be a well - known horror actor like Robert Englund if it's a Freddy Krueger - like monster.
I'm not sure who the specific author of a work named 'the monster at the end of the story' is without more context. There could be many works with this title or a similar concept, and different authors might have created them.
It could be about a story where there is a sense of anticipation and fear leading up to the revelation of a monster at the very end. Maybe it's a children's story that builds suspense as the characters move through various situations, and finally, the monster appears as a big surprise.
One way to watch it is to check if it's available for purchase or rental on digital stores such as Amazon Prime Video or Google Play Movies. Sometimes, you can find it there.