Even if Castiel patrolled around the prison and considered it as his to protect, lately he had been avoiding pretty much everyone that lived there - Winchesters included - as he tried to keep his temper in check. Dean and Sam had already been victims to it, when he had essentially shoved them both onto a wall for daring to leave the prison without informing him, and Castiel had refused to let others caught the wrong end of his wrath.
His tone wasn't angry now, though. Compared to how he had shown up to Destiny's new home, the angel now seemed relatively in control. His eyes darted towards the bottle she had just put down, but the action didn't last very long before he turned back to her the slayer. Soldier mode. Ever the soldier, he was there to report a plan of attack, and his whole demeanor said it. Because, deep down, Castiel would always be a soldier first.
"I was able to speak with someone who was able to give me a hint of something that could be useful against the Leviathans. And I need your help with it." There was no point in making small talk or delaying information. Neither one were in the mood for it, and Castiel had a feeling that Faith might attempt to shake the information out of him if he decided to talk in circles.
As it was, he wasn't sure how she would take the vagueness of what he had to say.
"On Saturday night a slayer and a wolf need to be at the corner of Hickory and Market Streets. It has to be on Saturday night, to greet the first September moon." He paused, to give her a chance to process the information. Castiel knew he didn't have to even ask her if she wanted to do it, or if she was willing to. The look on her face said it all.
"The Leviathans will reveal a weakness that night," he continued, "and when that happens, you have to take advantage of it and kill the ones that will be there. It can only be a slayer and a wolf that does this, Faith. No one else."