Based on Universal's Halloween Horror Nights Haunted House Attraction in 2023 as well as the classic monsters by Universal
Sets place after season 5 finale and before season 6 premiere, starlight is getting used to being forgiven for the crimes she has caused, she gets a chance however when disappearances start popping up in Canterlot and little did everypony knew that it was a group of monsters causing carnage and terror to Equestria.
"Paris, the city of light but underneath her bustling boulevards and noisy cafes silence is key and darkness reigns!"
Paris is seen with all its beautiful lights and sounds galore, however, there is a darker secret that lies beneath the city, that creatures of the night hide and plan underneath.
One of these was the Phantom of The Opera, he had been down there for a long time, he had escaped the law and stayed down there as he sang the songs that he enjoys while paddling across the water in the underground tunnels.
Over time though, guests started to take residence beneath Paris shut out by humanity and forced to stay under such as the Hunchback of Notre Dame who had been hiding there for a few months the phantom hid.
Another was Dr. Jack Griffin who was also on the run from the law and decided to go underground as well, he was also known as The Invisible Man and killed people while using his invisibility to his advantage and continued doing experiments which caught sight of the law.
The last one was Dr. Jekyll, who had figured out how to get someone's split personality out in the world after years of research, he tried it on himself and it transformed him into a monster and named his alt. personality Mr. Hyde after causing chaos and causing innocent lives to be lost, Jekyll realized his alternate personality had caused and decided to create an antidote to his personality, however, the law was now after him and forced him underground in order to continue his research to a cure.
After a while of making a dominant spot in the catacombs, the monsters were off doing their one thing as each one was focusing, the phantom was still wandering through the underground only coming to the surface for any type of food he could find he was master of blending in with the shadows, the hunchback sits alone eating the rats that live in the underground as well as other things, the invisible man experiments with a way to turn invisible still with his clothes on as he is only invisible when he is naked and Dr. Jekyll continues to try to find a cure as Mr. Hyde causes chaos and escapes the law with ease before returning to his area they were all doing their own things as suddenly a portal opens for each of them as they look in curiosity as they see what seems like an expanding of the catacombs and all four enters and wonder what else beyond the catacombs.
It was a peaceful day in Canterlot, the birds were chirping and everypony was having a good time as usual. The two royal sisters were doing their royal duties (duties.. Yeah funny). Twilight and her friends who were still defending Equestria have turned a Starlight Glimmer to the light and getting used to everything. It took longer with the village that she once enslaved all of their cutie marks and forced them to do the things they normally do but not being as good as before. Nonetheless, she was now friends with the mane six and learning more about “friendship” as time went by.
However, underneath Canterlot four ponies crossed through portals in the deep catacombs of Canterlot. It was the monsters and when they entered this world they became ponies themselves demented looking ponies at that. All separated, all four of the monsters looked at their reflections in the water and saw they had become colorful ponies. The phantom took off his mask and saw his scared face. This time the face was not of a human being it was a pony's scarred and demented face. The invisible man's shoes were gone and the only things left were floating clothes and a bandaged face with goggles. The hunchback was not much different; he looked the same even when turned into a pony. Dr. Jekyll was most curious; he looked like a normal pony doctor with a unicorn horn but he wondered what his alter ego looked like when he came out.
They eventually run into each other before deciding to walk together as though separated as this is a new world they have clearly entered and must tread carefully. The two doctors talk about how and why they went underground and both were fascinated by how both were able to make remarkable discoveries that ended up both of them on the run and perhaps could help each other in some way. The phantom mourns for the hunchback of his friend who was wrongfully accused of crimes that she did not commit. As they found what they believed was either the exit or the entrance but as they stood outside their eyes widened as they beheld a beautiful sight. They saw a world of trees all around and barely any buildings except for the buildings they looked up and saw Canterlot.
They saw the peaceful buildings of Canterlot up above and were still in shock. They thought and thought as they came with an equal goal in mind to punish. Why would they need to be punished? As well, it turns out that Celestia has allowed tours into the catacombs for Canterlot to become more of a tourist destination. They knew that they would find their hideouts and would be seen by guests and likely called ugly, a monster, and other harmful things. So they all decided to team up if any of them would come across them and make sure they didn’t come out alive.
However, they realized that there were unicorns and pegasi which would be hard to kidnap or even kill them so Dr. Jekyll proposed that he could sneak through, blend in, and find the right spell books to combat something they've never faced before. And if you are asking how they knew it was open to the public well, there were several signs stating that this was the exit and nopony was there yet because it was not open.
Dr. Jekyll walked through the busy area and saw how spectacular it was. When a group bumped into him it was none other than Twilight and her friends! (What a conscience….) Twilight apologized profusely while Jekyll stated it was fine as Jekyll looked at the group he noticed that the pink one was overly excited in a disturbing way she bounced to him and introduced herself as well as Twilight and the others then pinkie asked what his name was and blabbered on about a welcome party cause she didn’t recognize him until rainbow put a hoof in her mouth to quiet her. He introduced himself as Henry Jekyll and certainly a pleasure to meet them as he respectfully bowed twilight thanked him and asked where he was going he was wondering where the spell books were.
But then his question was answered as he saw the huge building and quickly said never mind and bid them a good day. Twilight was suspicious of how fast he left and had a feeling he was hiding something. The others thought that as well but Rarity admitted that he looked quite nice. Maybe try to have a chance with him. Jekyll found what he was looking for, not books but scrolls. He quickly ran towards the exit of the catacombs and entered he eventually found the group who was discussing until Jekyll arrived. The Invisible Man (or Pony) asked what took so long, and Jekyll replied “I ran into the defenders of Equestria and they are suspicious of me, we must make haste!” They all gasped and quickly they used a spell that would give them magic and increase their speed, strength as well and abilities. With abilities in hand (or hoof) they were ready to spread carnage to those who dared to enter their territory.
“Extra, Extra, Catacombs open to the public for the first time!” “Ponies skeptical due to disappearances of workers preparing it!”, said the newspaper boy. It has been a while, but the catacombs are officially open to the public, however the disappearances have not gone unnoticed. Celestia has been trying to figure out why the workers are disappearing but it is clear that she needs the help of Twilight and her friends. She wrote a letter to Twilight immediately and sent the letter to Spike. This was a situation that she had a bad feeling about and it sounded deadly.
Twilight was in her giant crystal castle as she was looking over things in the library
Spike: Don’t you think you should take a break soon? Spike asked.
Twilight: Sorry spike but- just as she was about to say anything else spike threw up a letter- it was from Celestia.
Dear Twilight,
I regret to inform you that something bad is going on beneath Canterlot. Multiple workers have been disappearing to prepare the catacombs to be open to the public. Their families are worried to death about them and why they haven't returned. I need you and your friends' help including Starlight Glimmer, as this may help build trust after you reformed her. I will explain everything else when you girls get here
Sincerely yours, Celestia
Twilight was interested in what was going on with the catacombs, from what she remembered it was abandoned for eons and now workers disappearing. She had a feeling that someone or something was causing the disappearances and may endanger the innocent lives that entered the new attraction.
Later she called the girls to the cutie map and held a meeting about the recent request.
Applejack: So what's going on sugarcube?
Twilight: Thanks for coming girls, recently Celestia has opened the catacombs as of late and there have been disappearances.
Rarity: What kind of disappearances?
Twilight: Well… we believe in basic terms they might have been murdered…