Lucifer had screamed as he fell into the Cage.
He didn't stop screaming as the seals were fixed in place.
Each time Michael locked one, the screaming became more distant, more muted, but it was still there.
Finally, when the last one was put in place, the Cage was silent.
Anael no longer heard her brother calling for help.
Gabriel no longer heard his best friend's pain.
Castiel no longer heard the sounds of his family's war.
Michael no longer heard his brother.
Millenia passed, and the angels forgot; thought their fallen brother had quieted.
But when Dean picked up Alistaire's blade for the first time
And cut into that first soul
And solicited that first wail of pain
And spilled that first drop of blood
The angels looked around in horror.
One of their brothers was screaming, somewhere far away.
As soon as he heard it, Michael realized he'd only been fooling himself.
Lucifer had never stopped screaming
And he never would.