Castiel lowered his head a moment, acknowledging her comment and silently thanking her for it. Really, it was remiss of him to not offer some kind of warning, but she seemed to be fine for the journey, and his concern for Ruby's wellbeing was still great. After what Buffy had told him, he was anxious to find her as quickly as possible.
He raised a faintly surprised eyebrow at the sight of Mordred. Interesting. Even with all his knowledge, he suspected there was still much he had to learn about this situation.
But later. When Ruby was safe.
He nodded slightly towards the young man. "Indeed. The sigils are designed to keep me from entering. It took a powerful demon to create them, that much I know. Removing them would allow me access to this place."
And removing them would have to be done by anyone but himself. Until they were gone, there was nothing he could do, not a circumstance he was ever a fan of.