One of my biggest crossover pet peeves is making no attempt to actually merge the two words together. In some crossovers, nothing actually needs to be done. For example, crossing Harry Potter with a standard crime investigation show likely needs nothing as nothing in either is likely to be incompatible with the other.

This generally is not the case in two different media featuring magic, and is why I can't recall any good Buffy/Harry Potter fics (ignoring "world" crossovers where characters from one reality go to another, which isn't what I am discussing here).

For example, in Buffy, most humans have some capability to do magic. But the magic is not the wand-waving type, being more like magic rituals in most but not all cases. This is obviously contradictory in a Harry Potter crossover as magic is clearly limited to a very small, mostly hereditary, part of the population. Similarly, if demons are so common as they are in Buffy, demonology would likely be a significant part of DADA at Hogwarts and demon/magical hybrids would likely exist as demon/muggle hybrids do.

At the same time, a world merger crossover should not shit on one of the fandoms. This is almost always a sign of a spite and/or "my fandom is better than yours" fic.

I'm mostly thinking about this from the perspective of a Buffy centric story with Harry Potter stuff coming in.

My thoughts broadly are:

Harry Potter changes:

Demonology as part of DADA.

Some part demon witches and wizards should exist (possibly treated in the same way as lycanthropy, so maybe rarely talked about?).

Dementors are part of the broader range of demons, summoned to this world by human misery (much like canon), but are visible to muggles like other demons are. Though perhaps the MoM enchants dementors in their employ to be invisible to muggles?

Scrap canon magical North America.

SoS is not harshly enforced on muggles that have dealings with demons. The main concern is preventing widespread knowledge of magic, similar to canon Buffy fears of widespread knowledge of demons.

Some muggles doing magic with "pre-charged" magical objects?

Buffy changes:

Willow and other canon witches are muggleborn witches. Warlocks will be replaced with wizards.

Most magic is similar to HP magic. Wands, potions etc. A lot more ritual stuff however, borrowing from Buffy.

Magical North America is highly Balkanised and the further West you go, the more it becomes the magical Wild West. This means that out West, most muggleborns slip through the cracks and never receive magical schooling. Most that do receive any education do so on an informal basis.

Most magicals in the West are descended from muggleborns, as without the muggle drivers that pushed people West (free farmland mostly), magicals were never highly motivated to emigrate that direction. They do get lots of tourists and thrill-seekers however, mixed in with exiles/criminals escaping law enforcement in their home countries.

Law enforcement in the West is primarily focussed on maintaining the SoS and is primarily conducted on an ad-hoc basis. Law enforcement is mostly conducted by elected sheriffs on a part-time basis.

Demons and magical communities mostly self-enforce the SoS out of fear that any large-scale breaches will see Eastern American or European magical task forces being sent to fix the problem.

Some demons like using wands, many don't need them. Most government prefer demons to not have wands (i.e. like the goblin wand ban), but this is less enforceable in Western North America.

The Slayer is always a muggle girl.

Justification/discussion:

Wild West - I don't think this is that unreasonable as the muggle Wild West ended in the 1910s. With a much lower population, I can see a magical equivalent lasting well past the 1990s.

SoS - Magicals have reluctantly accepted that muggles in some areas need to know about demons to deal with them, leading to less harsh SoS enforcement in some locations.

Slayer - mostly to force a collision of the magical and muggle world, and also justify the Council being mostly muggle. Something like the magicals grudgingly accepting that the Slayer is muggle business as she is an otherwise muggle girl.

Muggles and magic - Limited to small things and so the mostly muggle Council can do tracking spells and the like. Probably ritual based?

I was hoping to get feedback and hear other people's ideas on the concept. I haven't got much of a plot right now and am mostly thinking about the basics before diving into that.

 

Let's merge Harry Potter and Buffy in an enjoyable way?
Don't say 'penis in vagina.' Don't say 'penis in vagina.' Don't say 'penis in vagina.'
What about peni-

Well, the HP vampire lore would need to be excised, not that there is much of it; they don't even get an entry in Fantastic Beasts.
One would hope that even Slughorn would be smart enough not to invite a soulless demon to a minimally supervised (or, in fact, any) school party. Then again, he may have assumed the precedent had been set with Umbridge.

Willow and the like being full blown witches seems slightly iffy. Ignoring that, how do you explain magic 'addiction.' Like, what causes it? Only dark magic? Only so-called wandless magic? HP wizards and witches, even Molly, would scoff at the idea that tossing around lots of magic is a bad thing, given they even use it to scrub pots and pans, knit, and cook dinner.

I'd be tempted to say they can usually only do ritualized magic, because it allows them to raise their energy level to the point sufficient to actually cast something, but that doesn't really work because there's all of that stuff with people referring to Willow as powerful and her doing a bunch of very, uh, indiscreet free form stuff, particularly during her rampage (tearing someone's skin off being rather unsubtle). Unless one considers Willow an exception.

Spoiler

Edit: There are similar problems with HP/Anita Blake crossovers. First you have to explain why HP werewolves are so garbage compared to AB's examples. After that, there is the total lack of high-powered, casually casting, wizards in AB. They have witches, but compared to the ones in HP, they'd might as well be kids at a sleepover playing 'light as a feather, stiff as a board.' And then there is the muggle death sentence for using magic against people... Ouch. And, unless you want to suck a lot of the fun out of your crossover, you have to explain why either A: The vamps and weres knew about HP-style magic but never informed Anita about it or B: How the Wizarding World managed to keep themselves a secret from even the weres and vampires.

 

I'm not sure what you are arguing. Changing things is pretty much a given, and changing Willow's magic addiction is far from insurmountable.

Like, in the time it took me to write the previous line: Willow becomes addicted to some sort of magical aid that she started taking as to better help Buffy fight vampires. I.e. a potion or something. Perhaps something that makes he react faster or cast faster, but with dangerous side effects.

 

I wasn't arguing anything, just literally asking the question.

I'm not going to think of it for myself, all of my brainpower is currently being devoted to figuring out item injection through Leveled Lists in Fallout 4, and it is a losing battle.