When God commanded all angels to bow down to humans and Lucifer's rebellion, there was a fifth Archangel who chose to be reborn as a human to experience why Hod wants all angels to bow to them.

After centuries, you are born to Mary and John Winchester. Middle child of the family. You grew up as a hunter, and when Sam was killed, you took the deal before Dean could. You went to Hell and was raised by someone, someone who awakened your Archangel grace. Returning your memories and powers.

You immediately flew to Dean and Sam, who were in a motel. You went through all the tests and explained everything to them. They don't reject you and hug you close. You purify the demon blood from Sam and know in your grace that you prevented the apocalypse.

You are standing outside, settling your grace in your vessel when you sense a bond. One between you and another angel, which is very rare and revered for an Archangel to form a bond with another angel. You tug on the bond and wait for the angel to come.

Castiel had raised the Righteous Man when a shockwave of Archangel grace burst forth, shaking the foundations of Heaven. Michael and Raphael were ecstatic that their lost fifth sibling is alive. He is waiting outside of the throne room when he feels a tug on his grace. He follows it and appears before the Righteous Man ... who holds Archangel grace.