Infinity: Kill your way through the movie world.

“What a strange residual energy.” Sam squatted down, wiped the ground with his fingers, and picked up a layer of fine dark gold powder. The powder was slightly warm on his skin. “The concentration is very high. The owner of this energy stayed here for at least half an hour.”

They climbed the stairs, their footsteps echoing in the empty corridor. On the third floor, at the end of the corridor, the door to an office was ajar, a faint light shining through the crack.

Dean and Sam exchanged a glance, then stood on either side of the door. Dean held up three fingers and counted down: three, two, one.
Sam kicked the door open, and Dean rushed in, his gun sweeping across the room.

nobody.

But there was something in the room.

A complex magic circle was drawn on the floor with a dark gold liquid. It was neither a demonic rune nor an angelic prayer; it was a twisted, ever-changing pattern.

At the center of the design are three things: a half-burnt white candle, a black feather, and an ancient gold coin.

The gold coin has wing-shaped patterns engraved on its edge.

“This is…” Sam approached, but didn’t touch anything, “some kind of tracking ritual, he’s looking for something. Or… marking something.”

Dean's gaze fell on the wall.

There, a line of text was written in the same dark gold liquid, the handwriting messy, as if hastily penned in extreme pain:
"It's talking in my head."

Below the writing, there are several deep scratches, which, judging from their shape, appear to be fingernails. At the end, there is a piece of human fingernail embedded in the wall plaster, leaving a bloody mark.

Based on the online addiction's analysis of various residual footprints, energy traces, and behavioral patterns at the scene, there is a 98% probability that the mastermind behind the incident is Castio.

This statement also indicates that Castillo is indeed in trouble.

"Damn it," Dean growled, slamming his fist against the wall. "We should have found out sooner, we should have."

"It's not too late to find out now."

The sound came from the doorway.

His voice was slightly hoarse, with an upper-class British accent, each syllable as precise as if measured with a ruler, yet it sounded very familiar.

Dean and Sam's expressions changed drastically the moment they heard the voice, and they turned around at the same time, pointing their guns at the door.

Crowley stood there.

He was wearing a perfectly tailored dark gray suit, shiny leather shoes, and carrying a long-handled black umbrella, even though it wasn't raining outside.

He leaned against the door frame as if he were attending an afternoon tea party, rather than standing in the dust of an abandoned office building.

“Relax, boys.” Crowley raised his free left hand, palm out. “I’m not here to fight. Actually, I’m here to help.”

"Help?" Dean didn't lower his gun. "The King of Hell would help the Witcher? Am I still dreaming?"

“Former King of Hell, thank you.” Crow tapped the ground with the tip of his umbrella. “And, to correct you, I have ‘temporarily’ unified Hell but have not yet been officially crowned, so theoretically I am still a free demon merchant. Titles are important.”

Sam stared at him: "What do you want?"

“I want to stop a disaster.” Crowley entered the room, his gaze sweeping over the spell array on the floor, the writing on the wall, and finally back to the two brothers. “It’s about your angel friend and that unwelcome lodger in his belly.” Dean’s finger was on the trigger: “Explain.”

“It was in an abandoned warehouse on the outskirts of Sioux Falls, South Dakota.” Crowley’s voice was calm, as if he were recounting a weather forecast. “Casdeo and I worked together to try to open the Gates of Purgatory and absorb the power within. The plan was half for him and half for me. Fair enough, isn’t it?”

He paused, a smileless curve appearing at the corner of his mouth.

"But he lied to me. At the last moment, he used the Angelic Imprisonment Curse to trap me, and then... he swallowed all the purgatory energy, not half, but all of it, leaving me not a single bit, including that old monster that had been sleeping for tens of thousands of years."

“He has a good appetite; he can swallow anything.” Crowley’s tone was laced with sarcasm and heartache.

"What monster?" Sam asked.

“Leviathan.” As Crowley uttered the word, the room temperature seemed to drop a few degrees. “It is something that God sealed away with his own hands. It is neither a demon nor an angel, but something that is more ancient, more chaotic, and more pure. It has no concept of good or evil, only hunger—hunger for the soul, for energy, for existence itself.”

He walked to the wall and looked at the words.

"It is speaking in Castio's mind, which means it is eating away at his will, little by little, like worms gnawing on an apple core. Once it's done, Castio will cease to exist, leaving only a Leviathan vessel cloaked in the skin of an angel, a calamity walking among humans."

Dean's gun finally lowered slightly: "So Castio hasn't changed... he's just being controlled?"

“Control?” Crowley laughed. “No, worse than that, it’s fusion; the energy of purgatory, the souls of millions of monsters, the essence of Leviathan, all of these things are now mixed together with Castio’s angelic core, like a violently shaken poisonous cocktail. You can’t tell which part is Castio and which part is the monster; they’ve…mixed.”

Sam's face paled: "Is there a way to separate them?"

“Theoretically, yes.” Crowley turned to face them. “If Castio’s will is strong enough to resist Leviathan’s corruption, then he might regain control at some point. But that’s a gamble, the odds are slim, and with each day it drags on, Leviathan’s control deepens.”

He took a folded piece of parchment from his inside suit pocket and placed it on the desk next to him.

“This is a tracking spell, activated with your blood. It can lock onto Castio’s location as long as he is still in this world. The spell also contains a binding spell. When it hits him, it will immobilize him for three to five seconds. It’s a short time, but enough to do something.”

“Save him,” Dean said.

“Or kill him,” Crowley corrected. “To completely drive Leviathan out, the power needed is far greater than the two of you combined. It needs… well, someone who can simultaneously wield the power of balance and the power of the Antichrist.”

“Lore,” Sam said.

“Smart.” Crowley nodded. “But don’t expect me to go to him. That chairman… is too dangerous. When I stand in front of him, I feel like a frog being stared at by a snake. I have no chance of winning, and I don’t even have a sure chance of escaping. So you’ll have to deliver the message.”

He walked towards the door and stopped at the threshold.

"Oh, one more thing, Castio will be returning to that warehouse on the blueprints."

"Although the Gates of Purgatory are closed, there is still residual energy. Leviathan needs that energy to complete its final fusion. If you want to stop it, time is running out."

After saying that, he stepped out the door and disappeared around the corner of the stairs.

The footsteps faded into the distance. (End of Chapter)