Luckily for fans, we already know that Cas is coming back this season, so we don't need to mourn Misha Collins' resilient angel — but for the Winchesters, that loss is potent and, as far as they know, permanent.
"This profound sense of loss lingers over several episodes. He’s not coming back real soon, and it influences, greatly, Dean’s state of mind," says producer Brad Buckner, who was joined by his writing partner Eugenie Ross-Leming and star Jared Padalecki for a press screening of the Season 13 premiere before it aired. "Both the guys have had to rebound from stuff over and over and just kind of shake it off and go on with the family business, and this overwhelming loss at the start of the season is something that Dean just can’t dig his way out of yet."
That grief is compounded by Dean's feeling that the Winchesters are truly alone in this fight — as demonstrated by his desperate prayer to Chuck to bring back Cas and their mother, Mary, which once again went unanswered.Read more at Mashable