I love this idea . . .honestly this campaign could be as long or short as you want there is so much content to be inspired by. I also believe, there is a Buffy TTRPG out there, though it may be out of print now. And I love that more people are discovering the Buffy Movie, it's so good, it's such a good time Not to spoil Fantasy High at all, but it is not a boarding school, it is absolutely a fantasy high school with the kids still living with their guardians and interacting with the town. Diminsion 20 does have a boarding school series adventure as well in Misfits and Magic. But the idea for Fantasy High was what if an 80s high school movie (Pretty in Pink, Breakfast Club, etc) was in a world where the kids and parents have magic. So you very much could take some inspiration from it if you wanted more sessions to revolve around shenanigans happening in the school. Great Concept!

One plot point handy with D&D's Planescape setting: portals to the Outer Planes usually have some specific key to open them. Not necessarily a unique item or overly valuable. Can be a mundane item for a portal key, but is not something commonly carried every day. This is sometimes a point where a DM may get tricky, making the info on what the key is, itself a mystery to be solved. Also, I'm more familiar with 2nd ed. AD&D's Ravenloft than 5e, but it definitely has great monsters and scenery that's compatible with some kind of Dark Ages Buffy. For ex., the Ravenloft supplement of the Monstrous Compendium does a great job describing what happens to "demi-humans" when turned into vampires. i.e. Vampire elves, dwarves, halflings... :) Also, Ravenloft does have rules for "madness" due to exposure to excessive horror. This can result in mental illness not just on the individual scale, such as Jack the Ripper-like psycho killers ("Mad Men" in the Ravenloft Monstrous Compendium), but on a social scale as well. Events like mass paranoia (witch hunts), mass denial (no such thing as vampires), and other village-wide freak outs.

the one episodic Buffy i remember clearly as a concept is Beer Bad (bar owner hates frat boys, uses potion to turn them temporarily into cavemen). As a standalone session, think just having someone potion some of the other kids, and regress their mental stats would be interesting, especially if one of the party gets affected. As part of the broader plot, the bar owner might have made a deal with the Master to weaken certain students and make them more vulnerable to be taken as sacrifices; have more people be affected than the episode shows, and then the headcount at the end shows that some of the victims are missing. Another episode that is of interest to me is Superstar, where a loser the Gang used to know was retconned into being a powerful ally. It is later revealed that he used a spell to make himself strong and worthy of respect, but equivalent exchange meant that his insecurities and other faults were expelled and congealed into an "opposite number" that he alone cannot defeat, since weakening the creature would weaken him too, back towards NPC level. Might be fun to play with the choice of having this additional, powerful ally, but the creature will also exist somewhere out there, even sealed away, or returning things back to normal, and if this person would even be willing to do it. Also interesting to me to play the creature as a Lawful Evil, in that they only inflict equivalent harm for all the good that the NPC does.

speaking of Fantasy High, NADDPOD (which has two of the same cast members) had a vampire arc as well in Shadowfell. They also had a Feywild arc which was very fun too- both in campaign 1.

Can't recommend Fantasy High enough, and it sounds very much like the ideas you described. The teen adventure tropes meeting fantasy tropes is hugely fun. Love the 'unusual race as transfer student' idea. My GF had the exact same idea for a Tabaxi. And I've heard others cite Buffy as inspiration for episodic D&D games. It's easy to facilitate that 'monster of the week' vibe, or create season arcs too. Match made in heaven!

No spoilers, but the whole series can be a long, ongoing campaign, with each season being a main quest. Each season has a "big bad". A new evil to defeat until the end game.

my moms showed me buffy mabye a year ago, and i have been obsessed with an idea like this FOREVER SINCE

I love this! There’s a lot more ideas you’ll get from the later seasons of Buffy too:) I can also see doing this using the kids on bikes system.

Ou, I am very much interested.

It would be possible for multiple characters to start out as The Slayer. Trying not to give too many spoilers, since you said that you have only watched the first season so far, but in later seasons there are a number of occasions when there are multiple Slayers. Setting the campaign at a time when there can be multiple Slayers would allow all of the player characters to be Slayers, reducing the chances of one character being over powered and therefore the chances of main character problems From a D&D (or other RPG) point of view, being a Slayer should allow the character to detect undead and super natural at close range, say 5 or 10 feet per level, and any of the characters attacks count as being magical for purposes of over coming damage resistance, plus maybe resistance to some of special attacks of such creatures, and maybe some other things, I would have to re-watch Buffy to try to determine what other abilities she has. Whether a Slayer gets all of these abilities at 1st level or whether they would slowly pick them up as they level up is something I would have to think about when creating such a campaign. Other than that the characters would have your normal classes, so you could have a party of Slayers, but they all might have a different class.

I love buffy... would play that (one shot, 3 sessions or capaign) any time... 😂 sign me up...