Castiel's eyebrows knit together in confusion as Gabriel mentions that Claudia might show up with someone in tow. As he moves on to bring up his stint as God, he frowns, taking an interest in the ground. That definitely wasn't one of his finer moments, and he regrets killing Balthazar about as much as all the deaths of the other siblings and humans he's responsible for combined.

He looks up, though, as soon as Gabriel says that they needed a dead angel. "Did you find a way to bring Balthazar back?"