That's when Castiel shows up, and he's more than bewildered at what he sees: House's grace leaking out at edges of his vessel, adjusting itself, and then falling out of line again. He finds himself panicked, looking at the room with the snickering demon, then back at House before rushing over, pulling House away from Chase again again taking a look at the wounded arm.
"Turn away," he commands Chase sharply the moment his eyes catch a glimpse of House's grace billowing up at the wound.