Abomination(Supernatural AU)

Anzillu

"Jack! Breakfast!" Sam yells over his shoulder as he flips a pancake onto a plate. A head pops into the doorway of the kitchen in the Men of Letters bunker.

"Breakfast?" An eager Dean says delightfully as he waltzes into the kitchen and snatches up the plate of pancakes. He dumps a crap ton of syrup on top of them and grabs the top pancake in his hand and crams it into his mouth. 

"Really? Would it kill you to be a little civilized?" Sam sarcastically says while rising his eyebrows.  Dean shrugs with his mouth full and syrup dribbling down his chin. Sam rolls his eyes and turns back around to continue making more pancakes. 

Jack stumbles into the doorway scratching his bed head, eyes still half closed. 

"Mornin champ" Dean brightly mumbles around his food. Jack gives him a blank stare as he tromps into the kitchen to look at what Sam is doing. He stands by his plate as Sam refills it with pancakes, keeping an eye on Dean. 

Jack takes his breakfast and sits down at the table, letting out a long yawn. He grabs a plain pancake in his hands and starts gnawing on it with his eyes closed. Dean looks at him disgusted, 

"Dude, what are you doing?" He scoffs. Jack opens his eyes again with a blank confused look about him. "Here, use this. Makes them taste less like cardboard." Dean slides the syrup towards Jack who hesitantly pours a little bit over his half eaten piece. He takes a tentative bite and chews a couple times. Dean smirks to himself as he see's Jack's eyes glow as he takes another bite quickly.

Sam rolls his eyes at them.

"We have a problem" A gravely voice says in between heavy breaths.

"Jesus Cass!" Sam and Dean say together as they both are startled. All three stare at each other for an extended second. 

"Uh, we have a problem" Cass repeats himself as he nervously looks back and forth between Sam and Dean.

"What" Dean replies sharply.

"Lucifer, he's on the move again. He's been hunting down and torturing angels to find your location. I just barely missed him, we need an action plan to beat him." Cass explains clearly after clearing his throat.

"Right, because ganking a pissed off archangel who also happens to be the Devil himself is a milk run." Dean says dryly, leaning on the counter with one arm. "We don't even have anything in this entire bunker that could scratch the guy!"

"I am aware of that" Cass replies.

"Well, what is there that we could use to hurt him? The Colt, angel blades, and the demon knife don't work on him. And an archangel blade only works if an archangel is using it. What play do we even have?" Sam adds. Cass furrows his brow, deep in thought. 

"What about the Bible?" Jack chimes in, wide awake now. "I mean, Lucifer was cast out by God, shouldn't there be something there on how to hurt him?"

"Maybe not something, but someone" Cass said rubbing his chin. Sam and Dean look at him expectantly. "I've only heard rumors, but, Jack is not Lucifer's first born. Long before I was created, after Lucifer fell, he made the first demon. She wasn't just a demon, she was Lucifer's partner and companion. She bore his first born."

"Wait... So an angel-demon hybrid? Is that even possible?" Sam exclaimed in shock.

Cass nodded, "Yes, she was the Alpha of her kind. We called them Anzillu, it translates to 'abomination' in ancient Sumerian."

"Alpha? So there's more than one of these Anzillu things?" Dean commented eyeing Cass.

"No, they're extinct. No Anzillu has ever survived an entire day on Earth. It's the only time angels and demons work together. Anzillu are incredibly powerful, with the combined strength of a demon and angel on steroids, they would be unstoppable if not for their several weaknesses. They can be hurt by holy water, salt, angel blades, devil traps, warding sigils, and Holy fire. This makes them very easy to kill" Castiel continues to elaborate.

"Ok, so if they're extinct then why are we even speculating about this?" Sam chimes in, crossing his arms.

"We have records of every Anzillu's death except one, the Alpha. She has been long forgotten, some even believe that she doesn't even exist. Others say she's dead because if she wasn't then she would have showed herself by now. But, if she does exist then she's our best bet to beating Lucifer."

Sam, Dean, and Jack all exchange skeptical glances.

"How would we even find this Alpha Anzillu?" Jack asked,

"If she's half angel then she can hear prayers right?" Dean questioned, Sam cocked his head a little, worry flashing in his eyes. "What's her name anyway?"

"Alyssa"

Sam, Dean, Cass, and Jack all froze in place. Jack's eyes were fixed on a mysterious figure leaning against the doorframe to the kitchen. Sam, Dean and Cass turn around to face the mystery woman. 

Her eyes were so unsaturated with color they looked almost grey, like a corpse. Her hair was a reddish brown, long and straight. She looked just like a normal human, yet her skin was washed with a grey color making her look even more like a corpse. She fixed all four with her cold stare, no expression showing. 

"Castiel, you dare speak of me? How brave of you, little bird" She sneered to the angel. Cass shuddered at his name being spoken. Alyssa gracefully walked down the steps and stopped a couple inches away from Castiel's face. Before she could speak again Jack shot up from his chair, 

"Get away from him!" He yelled sternly, his eyes glowing a warm yellow.

"Oh? A Nephalim? Alive? How curious," Alyssa murmured not breaking eye contact with Castiel. "You let this vermin live? What has become of the angel's honor?" She chuckled softly turning her gaze towards Jack.

He flinched and unleashed his grace upon her. The waves of power concentrated on her lithe body. Alyssa sighed boredly and flicked her hand, sending Jack flying into the wall. His body flung through it and into the next room. 

Sam and Dean's eyes widened in fear, Jack was supposed to be the strongest being in existence, yet Alyssa just swatted him like a fly. 

"Why don't we all sit down and chat before we go slitting each other's throats. Shall we?" Alyssa said calmly, raising an eyebrow in Sam's direction. Alyssa snapped her fingers and suddenly all five were seated in the library in the bunker. 

Alyssa propped her feet on the table, "So, you're going to ask my help to defeat Lucifer because he's trying to destroy the world. Or something" 

"He's after his son, Jack" Sam responded glancing at Jack who, for a guy that just got thrown through a concrete wall, looked pretty good.

"Ah, and why would I help you insects? Fortunately for me this isn't the only world in existence, so I should care about your problems why exactly?" 

"You tell me, you came here. And Lucifer is your father, which makes Jack your half-brother" Dean retorted quickly, Cass and Sam whipped their heads around to stare astonished at him.

Alyssa cracked a smirk, "Well, look who grew a pair. But how would you know that I'm not here to do Daddy's dirty work-"

"Because you hate him, just as much as we do. Maybe even more" Dean cut her off, stepping in between Sam and Alyssa. "You were thrown out like yesterday's garbage by your own father. And now you have the perfect setup to get your revenge." 

Alyssa fixed Dean with an intense gaze before she looked away, starting to circle around the room.

"True, I couldn't approach him during the apocalypse, can't take on two archangels. But now that the archangels are dead and the Satan spawn is safe with you," she smiled widely, "I'll make sure he knows exactly what it's like to have everything he's ever known ripped away from. And then he'll rot for all eternity like the useless lump of meat he is."