One cliffhanger could be the main character suddenly seeing a pair of glowing eyes in the darkness just as they think they are safe. Another could be a door slowly creaking open on its own when the protagonist has just started to relax. And a third could be the sound of a strange chanting starting up again just as the sun is about to rise.
One could be the main character suddenly hearing a strange noise right outside the supposedly safe room they've barricaded themselves in. It leaves the reader wondering if the source of the noise will break in and harm the character.
Cliffhangers enhance the end of a horror story by leaving the reader with a sense of unease. For example, if the story ends with a character being dragged into the darkness while screaming, the reader is left imagining all the horrible things that could happen next.
They create anticipation. Let's say a horror story ends with a character looking into a mirror and seeing a strange reflection that starts to move towards them. This makes the reader eager to know what would happen next. It also makes the story more memorable because it stays in the reader's mind, like a nagging question that they can't shake off. In a way, cliffhangers can make the horror feel more real and immediate as the reader is left to fill in the blanks with their own fears.
One good cliffhanger could be when the main character is about to open a mysterious door and all you hear is a strange noise from behind it. The reader is left wondering what's on the other side and if it's something dangerous or amazing.
A sudden noise outside the door that the character can't explain. For example, in a haunted house story, the main character hears a scratching sound at the door, and just as they are about to open it, the story ends. It leaves the reader wondering what's out there waiting to come in.
In 'The Hunger Games' trilogy, at the end of the first book, when Katniss and Peeta are both declared winners but the Capitol seems to be up to something. It makes you wonder what will happen to them next. Also, in 'Harry Potter and the Goblet of Fire', the end where Voldemort has been resurrected and Harry has just escaped. It sets up a whole new level of danger and mystery for the subsequent books.
She thought she had escaped the haunted house. But as she stepped onto the porch of her own home, she felt the same icy grip on her ankle. The horror had followed her home.
One of the books with a huge cliffhanger is 'The Da Vinci Code' by Dan Brown. The ending leaves you with so many questions about the secrets and mysteries that still seem to lurk in the shadows, even after the main plot has been somewhat resolved. It makes you wonder about all the possible implications of the things that were discovered in the story.
In 'The Girl on the Train', the cliffhanger at the end of the book where the truth about what really happened on the night of the murder is only partially revealed. It keeps you guessing about who is truly responsible and what other secrets are still hidden. Also, in 'A Tale of Two Cities', Sydney Carton's self - sacrifice at the guillotine is a huge cliffhanger. You're left thinking about his final act of heroism and the impact it will have on the other characters.
Ending with a sense of unresolved mystery can be effective too. Maybe the source of the horror is never fully explained, like a strange noise in the attic that just stops, leaving the characters and the reader in a state of unease, wondering what it really was. This makes the horror linger in the reader's mind long after they've finished the story.