I was fairly new to D&D, I still am as I've only ever played 2 campaigns. But I tried my hand at DMing (my friends were skeptical at first, until they heard what I was planning).
Bit of backstory to set the scene. I volunteer at a haunted house that is put on by a charity organization. People pay to go through and get scared out of their minds, all the funds collected go to the local school for people with disabilities. I've been doing it for YEARS, and so have a couple dozen others. We all are friends and around the same age (all within 3 or 4 years of being 20) and a pretty tight knit group that keep in touch on haunt offseason via a group chat. Eight of us all decided to form a D&D group, after finding out we all play/are interested in playing it. I had never played before but was super exited to. We play 2 premade campaigns with one of the more veteran players DMing (one of them was Curse of Strahd).
All the while, I'm thinking up my own Homebrew Campagn (I called it The Paxton Escape, as the haunted house we all volunteer at is called Paxton Manor). The basic outline of it is that the party is a group of "customers" going through the haunt like how it goes when it's running. The only thing, its not actors jumpscaring and screeching out lines, its real. They have to battle and solve puzzles and each of the 32 rooms in the manor is a new encounter and based off of the actual rooms. I spent months planning everything. Ghosts or little orphan boys (the manor used to be an orphanage), a haunted painting of the original owners (pops up throughout the house, basically works like shops cus they sell stuff that help the players), demonicaly possesed people who failed to get through the house (based off of the organizers of the haunt), a cannibal chef character from the haunt, a doctor out to harvest your organs from the haunt, a small group of little girls who are just a little unsettling but tell you things you need to know, classic pitch black room with "something" in it (it was a skeletal poisen dragon, also from the actual haunt), a continuously changing maze of course, a series of rooms filled with creepy clowns that would ask you riddles or give puzzles or force some kind of saving throw on the group, a broken animotronic grim reaper that if fixed would join as an NPC and was basically a nerfed necromancer (could only summon 1 undead thing per long rest and the chill touch cantrip) who everyone got very attached to (also from the actual haunt, his name in both places was Difter, from the acronym DFTR, from the song Don't Fear The Reaper), the infamous elevator and elevator operator (worked like the mystic elevator from the board game Betrayal, could be summoned once per session by Difter if majority vote said yes, I'd roll 4 D8s and the sum would be the room they were taken to, first 4 rooms were left out because they're all very low level and setting establisment) the operator was also a sort of backwards merchant, he delt with magic items, but didnt take gold, no, you bartered with him, he was also kinda not to be messed with so you better not lowbar bartering a used sword off a skeleton for a magic septor, otherwise he'll override the elevator and fight you (win, and the elevator continues and you get your trade, lose, and your downed and dropped off at your room, either outcome and he wont trade with you the next time he is summoned, but then returns to normal). Get dropped off in a room you've already been through, gotta do the encounter again (although the enemies are only half hp this time), get dropped off in a room so that you skip a few? Hope to god it isnt a super hard encounter. Yes you can rest on the elevator, but it has to be decided before you call it. Yes you can rest in the room after you clear it (some exclusions, like the maze).
I allowed anything goes on classes because whatever, tho everyone was human (its supposed to be the haunt made real, all of us were human… I think). We had a ranger (gunslinger), a rogue (theif), another ranger (monster hunter edited to be ghostbuster), a monk varient – priest (dont know where he got the class info, it was fairly balanced and was helpful against demonic enemies via divine damage), a bard (kinda sorta healer), a very tank based fighter, and a warlock (cultist-like). Party dynamic was great, priest and cultist playfully butted heads via trying to convert each other. The two rangers had a big bromance going on. Bard ended up successfully seducing Difter and they got in game engaged (had to come up with some super mushy edgar allen poe like wooing stuff, it was hilarious and cheesy and fun). Theif kept stealing shit from people, I may or may not have encoraged it. Fighter guy was kinda edgy, on my own type but ended up having the hidden heart of gold and very strategic, saved the party a lot of times with the riddles and puzzles.
BBEG ended up being the serial killer Carver family (also from the actual haunt) consisting of a insane dad (low hp, high ac, socerer based), a cannibal mother (high hp, low ac, barbarian based), and two chainsaw wielding twins (med hp and ac, fighter based).
Everyone had a blast. And it goes down in history as our best campaign. I still like being a player over DM, but DM is fun. We might go again with new characters and I'll change up the puzzles and riddles. Maybe add the Basement level in, and toss in some new surprises. Or maybe someone else will DM off my notes from the last game and I'll get to play as a character.