Supernatural fic. Dean/Fem!Cas pairing. Set in the A/B/O 'verse. Tormented Alpha, Dean Winchester, is so tired of fighting his primal side. The docile little Omega with the striking blue eyes is so determined to heal him. To take away all of his pain. But how could she manage that? Even if she could, there's no way Dean would allow her to carry that burden. She was his mate. His Fated one. The big angry Alpha fell for the small vulnerable angel. That was never supposed to happen. But it did. Will Castielle's sudden heat cycle be his undoing?