User blog comment:Tommy,Klaus&Kol2012+/A theory about the empty guardian/@comment-31057575-20181213193152/@comment-10889355-20181213223850

The Shadow is the oldest entity that we know, and in this show, if you’re old, you’re powerful. We haven’t seen much of The Shadow’s backstory so it is too early to speculate stuff. God may have rebuilt Cas before he reached The Empty... who knows?