Pre-2016, rewritten 2023
He planned to avoid this happening. His line of work came with risks, including that once something did manage to kill them, it wouldn't be the end of their suffering. For some of his marra, it was the beginning of something far worse. Demons like to play with their food.
Oak wasn't stupid. He planned, prepared, and kept his deals clean and debts paid. No one owned his soul but himself. The problem was two beings could interrupt a soul's passage to the beyond, and the smell of rotting eggs revealed that answer. He twitched his nose and refused to open his eyes. Stubborn, despite his confusion, but he did die. He remembered that. The details got fuzzy.
A demon had stolen his soul.
The motivations for that were pretty slim and, realistically, revenge. Dead; he wasn't much use anymore.
Claws raked through his hair and settled more around him. He was in the lap of someone. The rotting eggs overpowered any smell of that he might know. "I know you're awake so that you can open those pretty orbs of yours, sapling,"
His eyes opened more from horror than obedience. Any hope that someone was pulling a cruel prank died as the painfully familiar smirk of Zeb rewarded him. Fully demon and reclining comfortably in their nest, Zeb kissed his forehead, purring. The rumble rocked against his skin, and the claws started to hurt.
"You," Oak didn't have the words. What was there to say? Zeb would do something like this. He liked breaking the rules and shocking people with how much of a monster they were behind the pretty looks they wore.
"Me," agreed Zeb, voice too happy and smile too bright. Bloody hell, Zeb was high on sated bloodlust. He fed recently and well. Zeb fed on hate and fear, not so much of flesh. Something terrible happened. "You are my favourite. How lucky were we that I was around when you croaked it? I dealt with the people who did it, swept up your soul and now here we are."
Another awkward affectionate gesture, this time a bump on the head. It hurt, a touch too hard. Oak pulled Zeb's claws out of his hair and sat or tried to. His muscles refused to cooperate, and he flopped uselessly over Zeb's legs.
Zeb laughed, rubbing circles on his back. The sound grated against Oak's soul.
"Easy, it's not been a full week yet since you sacrificed yourself for the better good," Zeb rolled his eyes as he captured Oak again to help him up to sit. His claws caressed him gently but with ownership. Zeb's heat seared against his skin as he rested against Zeb for support.
"I refused any deals involving my soul."
Zeb's eyes narrowed, and his cheerful demeanour faltered. A claw tapped against Oak's chest with enough force to hurt. "I'd be happy if I were you. Your soul is tainted. Too much time playing hero and failing to hit the mark has you condemned to hell. I stopped that."
"I died," Oak agreed, not missing how Zeb defended his actions. "You didn't like that."
"Crossover can leave people confused," Some of Zeb's annoyance bled out of his shoulders, and he threaded an arm behind Oak's waist. "Maybe you should rest more."
Oak glared. Zeb's grin turned mischievous.
"I died, and you avenged me. The others, are they alive?"
"Still breathing when I left. The blue one tried to make a deal to return you. I refused. I didn't think you'd want that," Zeb stretched, his tail and horns moving in the gesture. If demons could blush, Zeb would be. They didn't like being soft for any reason.
Oak did not reach up to check his forehead for bumps. That would be the first clue as to whether Zeb started his transformation into a demon. He wasn't ready for that answer and needed to hold back the panic until he had more answers or a clue about Zeb's motivations. More memories returned. Seb snatched his soul from the gates of hell. Some idiot decided to start the end of the world by unleashing the denizens of hell on the material plane. Most noticeably, by waking up a sleeping god, which was about the point Oak got involved and a mortal needed to sacrifice themselves to keep the damned thing asleep.
"Did they close the portal?"
"You did. You threw yourself at the doorway, not knowing where you'd end up. The auction screamed when your soul failed to appear in its stands. Fools are the best companions."
"If I had better opinions, let me know."
Zeb laughed, nuzzling at his cheek with a gentle rumble. "Silly little plant. You had opinions; you didn't want to take them. I would have closed the gate and let you live as long as you allowed yourself. So, you could have asked any of the demons you flirt with, but you picked death instead."
"Picked would suggest I would ever consider making a deal."
"Sapling," the disappointment dripped off Zeb's words. It stung. "Regardless, I have you now. You're mine." Zeb kissed the crook of his shoulder, hungry and with teeth pressing to his skin. "Mine to keep, mine to feed, mine forever."
Oh fuck. This wasn't about his soul. Zeb wanted his full being, not his essence. The horror inside Oak shifted. He took a few breaths and tried to calm down. Things moved weirdly. His shoulders clicked, and he stretched his fingers to stop himself from clenching his fists. Sound buzzed strangely, and his chest ached from it. Zeb wasn't the worst of the demons he interacted with, but Oak never guessed that led to Zeb wanting him. His soul, sure, demons fed off those, but a person's essence was different.
"Sapling?" Zeb hugged him closer, tugging some more pillows around him.
"Everything feels weird," Oak said, not lying. His skin vibrated with the other world. His heart continued to beat, but his head ached from it.
"That's normal. It would be strange if it didn't. I'm unsure how long it'll take to settle into your new form."
"Is there a time limit?"
"Not particularly. I could do with sleeping a while. Everything got so busy and complicated upstairs. We could both do with a rest," Zeb yawned.
"I like that plan," Oak let the bed swallow him up, "We can sleep, and on the next adventure, we'll have new people to meet." And his friends and allies wouldn't have to see him as a demon. What would a demon with earth magic look like? Unless his card up his sleeve vanished with his humanity. Oak was his name; he'd been named for the tree outside his mother's hospital window. She wished him to be strong and protect the people around him.
He died to keep a sleeping god asleep and a portal sealed.
Zeb owned his soul and liked him as him. If they stayed now, it would be awkward for everyone involved. He didn't want to hurt his friends. He turned into Zeb and slept.