"Castiel, you said you were here to help." Before taking action, Dean deliberately addressed Castiel, while discreetly giving Sam a look. "Can you handle the thing in there?"
"We may need it alive to ask it some questions."
Understanding his meaning, Sam secretly adjusted the strength of the demonic power he was preparing to use, weakening it so that it would only restrain the demon inside without killing it.
They intended to use this opportunity to force Castiel to reveal his true background.
At this, Castiel merely nodded calmly and walked toward the basement's tightly shut iron door. He did not even take an attacking stance. He simply extended a hand and pressed it against the rusted door.
Then, a sudden change occurred.
There was no incantation, no runes, not even any obvious energy fluctuation. Yet the instant Castiel's palm touched the iron door, it was as though an invisible bomb of holy light had been thrown into the entire basement!
"Roar—!"
The demon's pained, terrified roar came from inside, mixed with an incredulous scream. "No, the light... It's you? How is that possible?! Heaven has never—"
The roar came to an abrupt stop.
Through the iron door that had suddenly flown open, Dean and Sam clearly saw the vicious demon. After a complex and majestic rune made entirely of pure light flashed past, its entire body was instantly erased like something wiped away by an eraser, dissolving into a wisp of green smoke. All that remained were the unfinished sacrificial array on the floor and the faint smell of sulfur in the air.
And at the very instant the light was at its brightest, the two of them seemed to glimpse the vague outline of a pair of enormous wings unfolding behind Castiel—wings made of pure light and shadow,