Description
My friend and I have been watching Supernatural lately (we're on season 5, no spoilers) and when I recently saw this picture set syblatortue.deviantart.com/art… show up on my tumblr dashboard, it made me start contemplating a Homestuck Supernatural crossover, and ended up drawing this because everything I touch turns to Johnkat.
My idea is really lame and stupid and will probably make zero sense to everyone who's actually up to date on Supernatural.
John is a holy robot angel just minding his own business and following orders like a good little soldier. From time to time he watches the humans to keep tabs on them and all and one day Karkat attracts his attention. He watches his life unfold for a while until something horrible happens, and despite Karkat's best efforts, all of his friends die. Desperate and with nowhere else to turn, Karkat makes a deal with a crossroads demon to bring them back, but at the immediate cost of his own soul. Like every other damned soul, Karkat's put on the rack and carved into in hopes that one day he will surrender and take up the knife himself, but in spite of everything, his will holds strong and for years and years he resists. Hell definitely turned him into something inhuman, but not from taking up the knife. It was from eons of suffering. Grief and pain can change you just as much as fear and anger... And on the rack every day as Alistair carves him up, Karkat just repeats over and over "I forgive you. I forgive you. I forgive you." and somewhere up in heaven it makes John cry.
And John watched from heaven, waiting for this poor, pure soul to break, and after the first few hundred years (hell years, not earth years) he starts to gain curiosity and interest. Karkat takes it because he honestly believes he deserves all the torment and that makes John so sad and he wants to help, but he's not allowed to intervene. After Karkat's been suffering for like a hell millennium or something (fucking long time like maybe 50+ Earth years) John starts getting fed up and when none of his brothers will do anything to save this pure, valiant soul from the pit, he decides to do something about it himself. When the demons and tortured souls escaped hell when the gate was opened, there were a lot of beings crawling out of hell, and a good number were not demons. That’s when John goes to the surface. Of course disobeying like that gets him in shitloads of trouble and so he and Karkat are together on the lamb from both Heaven and Hell, much like the Winchester gang.
The point of his defection is that in spite of trying to stay loyal and all, watching Karkat changes him and he begins to feel emotion, and by the time he defects he's so full of emotion he's been hiding and he lets it all out at once and the other angels would just be like "What the fuck was that?!" He does a pretty good job of hiding it until he finally decides he's going to defect. Unfortunately though, because he defected this means he has to leave Karkat alone a lot to fend off angels and lay down protective and conciliatory sigils and stuff to keep Karkat and himself safe. It's while he's out working on his protective barrier that the Winchesters find Karkat, mostly tipped off because Cass found the Enochian warding sigils and figured there was something big and bad in there that Lucifer didn't want the angels finding.
tl:dr Hundreds of years of torture in Hell turned Karkat into a troll because of his endless suffering and refusal to torture other souls in return. When Karkat finally escapes Hell, John defects from Heaven to protect him. John's efforts at keeping Karkat safe, however, attract the Winchester gang and fights, drama and/or shenanigans ensue.