Harry Potter x Danny Phantom Prompt
I do not support JK Rowling, but I was reading a fanfic earlier and one of the characters said that the Black Madness is actually obsession, that they are all more or less obsessed with/about something.
That got me thinking.
What about a Harry Potter and Danny Phantom crossover?
What if, many, many years- maybe even centuries- back, a Black married and reproduced with a halfa (it could even be Danny, if you go the time shenanigans route)?
That Black- let's call them Celaeno- would probably have to have been an only child or that their sibling/s died before having children so that the "Black Madness" spread throughout the entire family.
So, Celaeno met the halfa, they fall in love, maybe marry, and they have children.
The children are roughly a quarter ghost, and maybe it's not super dominant in some of them.
If the halfa sticks around, they could notice that their children are showing signs of Obsessions, and help them figure out how to manage it, which could allow you to add cool lore and Black Family Traditions, such as that being how Occlumency was started, for example.
Or we could say that the halfa left or something before that and their poor management of it caused the "Black Madness" to be so infamous.
The Black family spreads, growing larger. The genetic portion of them that is ghostly is probably very small by this point, but the Blacks are rich in canon-present, and who knows how long they've been rich?
What if they bought properties and make them into Black homes, and their surroundings become ecto-infused by their liminal presence and it becomes a loop of subsisting off of their own ecto that they produced, which very well could make them more mad.
And then, when they die, they become ghosts. Whether it's the type of ghosts we see at Hogwarts or in DP, or some combination, it's up to interpretation- you could even say that Hogwarts only has "tame" ghosts and the DP-style ghosts just exist out there- but if they are DP-style ghosts, that would help infuse the Black properties with more ectoplasm (or make it scarcer?).
This could also lead to an incident of a terrorizing ghost that leads to them having specific burial rites to prevent it from happening again, and you could do several interesting things with this.
Regulus, of course. With the interaction between his liminality, the potion, and the Inferi, he could maybe come back as a full DP-style ghost.
And, the Black family gets very scarce by the end. What if, say, Walburga's funeral got handled by a non-Black, or at least an only-barely-Black-affiliated-person, and the specific Black family burial rites are dismissed in favor of more normal ones?
What if the reason they can't remove her portrait is because she's possessing it?
It could be a 5+1 in 'five times one of the phantom crew had to deal with a Black + one time they managed to do so themselves'?
This could go one of two ways: this is set before the second Wizarding war, either pre-canon or early canon, and… Let's go with Tucker… Shows up in the middle of Sirius being arrested.
He goes "what", because his Obsession is clearly revenge? And the guy he went after is right there, running away? Why aren't you going after him? Plus, the way he's supposedly admitting that he got his friends killed, that is clearly him blaming himself for something that isn't his fault. Are you all idiots?
Option two! Tucker shows up in the department of mysteries, mid-battle, groaning about how he's lost and his baby is malfunctioning, looks up to see Bellatrix, clearly insane.
That is, to outsiders. To him, he sees a starved liminal desperately trying to fulfill her Obsession.
He throws her a thermos full of ectoplasm, and she looks at him in confusion, temporarily knocked out of her rage, and he mimes opening it.
She does so, and then guzzles it down. Once she's had her fill- and everybody had stopped fighting, because Bellatrix Lestrange had done so and was acting weird- she re-caps it and tosses it to Sirius, having been interrupted before she killed him, and, well, they're cousins.
As he repeats her actions curiously, she relaxes and her hair smooths from the frizzy mess it had been in ever since she had joined Voldemort.
Sirius relaxes, too, after having drained the rest of the ectoplasm in the thermos. He looks less gaunt, the ecto having helped him more than anything else had since he broke out of Azkaban.
Everybody just kind of looks around before resuming fighting, though noticeably more playful for the two Blacks.
Tucker makes his way out unnoticed in the chaos, recovering the thermos, from where Sirius had dropped it, on his way out.
Depending on when in the main of HP canon you are, the living Blacks are Sirius, Bellatrix, Narcissa, Andromeda, Nymphadora (Tonks), and Draco, with possible cameos of Walburga and Regulus.
