Came back bc fic idea wiggled into my mind
Essentially a Supernatural x Hazbin Hotel crossover, taking some inspiration from @kitsunesongs' Double Entry AU, specifically Fatherverse Lucifer again.
If y'all don't know Supernatural lore, I'll explain some to you because some of it seems VERY similar to Double Entry's fatherverse, with smaller key differences. (On that note, this may be spoilers for Double Entry so READ THAT FIRST, GO READ IT, GO!)
In Supernatural, instead of Roo, God wages war against Amara, his opposite, who cannot resist destroying anything he creates. Like Double Entry, God locks Amara away, except in Supernatural he leaves the lock with his most beloved angel, Lucifer. This lock is a Mark, and God has essentially cursed Lucifer to be slowly corrupted by Amara's influence over time.
It is this influence that ultimately led to Lucifer's rage, envy, and disgust when God created humanity and told the angels to bow to them. It's this influence that led to Lucifer refusing to bow and leading a rebellion. Those feelings would have still been there most likely, but nowhere near as deep without Amara whispering into his ear.
NOW. Back to the story idea.
Alastor gets transported into the Supernatural universe as a disembodied soul in Hell, but this is in the wake of his original universe being completely destroyed. Not because of Roo like he and many others had been expecting, but because God was frustrated and just decided to destroy EVERYTHING. A whole universe, gone. Lucifer, Charlie, Vaggi, Lilith, his MOTHER, they're all gone, as though they never existed to begin with.
Alastor only survived because Roo liked him. And Roo liked him because unlike others, who she could only influence, whisper to, nudge along, she could SPEAK with him, and he could speak back without being corrupted. Almost as if he was made to be able to do so.
Perhaps he was, and this was God's mistake. Because it left Alastor with abilities that essentially allowed him to be a multidimensional blindspot, so long as he was trained to do it. And oh, of COURSE Roo trained him to do it. Anything that could potentially fuck over her jailor at some point in the future.
Unbeknownst to her, it's her teachings that allowed him to escape. And it is her teachings that allowed him to eventually reconstruct a body. Not the one he had in Hell previously, apparently the rules in this new universe don't allow appearances like that yet, but he could reconstruct his human body. It was a slow process, of course, but that meant very little, because time was extended in Hell, and the place seemed rather... barren. Nothing around to disturb him.
Once his body is constructed, he wanders around, and finds he doesn't quite like how THIS Hell is structured. Naturally, he does something about it, starts moving things around, shifting things, and in his slow exploration and organization of this empty Hell, he eventually comes across a Cage. One with a being so immense, so bright, he instantly realized based on biblical scripture who he was looking at.
The Light Bringer. The Morning Star. The Serpent.
A marked being whose mind is being warped... Well, lucky for him that Alastor can do something about that, with all his teachings. Of course, this Lucifer still thinks humans are filthy unworthy creatures, and Alastor truthfully kind of wants to punt his stupid face regardless of how enormous and unfathomable he is, (which honestly Lucifer is a little stunned by, what the fuck is wrong with this human??) but, well, Lucifer wasn't wrong for being angry at being told to submit.
Alastor's from the Jim Crow era south, he can understand the ugly feeling of being told you are LESSER, that you must bow your head to another. Lucifer just has a nasty problem of falling a little too close to the tree, because like God he ALSO seems to have an egomaniac problem that makes him think OTHERS should be considered lesser... (And Alastor can see that this attitude was exacerbated by the literal curse that God placed on his own damn kid, Yikes.)
Luckily, Lucifer's in a cage, and Alastor has all the time in the world to poke him back into having a brain. In fact, he has more time than he would have in the previous universe, given that time is MUCH slower in this Hell.
(Alastor could have totally just left him, but Lucifer is currently the only other being in Hell, and unfortunately Alastor already has a taste for Annoying Lucifer Specifically, even if this is a different version of his favorite mockery victim.)
This is essentially a canon divergence that leads to Supernatural verse getting a more Hazbin edge to it, in that Alastor "discovers" a way for holy and demonic beings to make themselves bodies without having to steal it from others (leading to a Hazbin Lucifer appearance), his direct influence leads to Lucifer creating the Seven Deadly Sins instead of the Four Princes of Hell, and Lucifer ABSOLUTELY becomes a major simp because Alastor Does Not Leave Him Alone, and he is, unfortunately, extremely charmed by this impossible human, despite all the teasing and mockery.
Because of Alastor being a blindspot, no one sees that he's essentially completely derailed all plans of the Winchesters being used as divine flesh suits and shattered any prophesies by way of giving Lucifer the ability to make whatever body he wants. Alastor's existence in the universe stops a lot of things really! He even prevents his birth in this universe by killing his shitbag father before he gets his horrible grubby hands on his mother. No doubles, and his mother remains safe and happy!
At some point he does tell Supernatural!Lucifer about the other universe, about how God simply decided to destroy everything on a whim, including this other version of Lucifer and Lucifer's daughter— and S!Lucifer quickly picks up that Alastor is genuinely upset about the destruction of this daughter. Because she shall NEVER exist in this universe.
To which S!Lucifer is like "bet" and decides he's going to get this human pregnant the second he escapes this cage. In fact, does he need to escape his cage, they could totally do it through the bars, c'mon darling he'll SO give you that baby girl, ask and you shall receive—
(Alastor also mentions other Lucifer's failures as a parent and S!Lucifer is like "I could so do better" but that definitely comes with a LOT of discussions and arguments and convincing.)