'Supernatural' season 12 news, episode 10 spoilers: The past catches up with Cas; Mary to alter group's dynamic

Castiel's (Misha Collins) past will be catching up with him, and he will need Sam (Jared Padalecki) and Dean (Jensen Ackles) to keep him safe. Meanwhile, Mary (Samantha Smith) has returned to hunting to be with her sons, and this changes their group dynamic.

In the upcoming 10th episode of "Supernatural" season 12, titled "Lily Sunder Has Some Regrets," Castiel will be hunted by someone who has wanted revenge on the angels that killed her family for a very long time now.

The synopsis reads: "Lily Sunder (Alicia Witt) steeps herself in black magic, honing her powers for over a century, waiting to exact revenge on a band of angels that murdered her family. Sam and Dean must work quickly to stop Castiel from becoming her next victim."

Collins shared in an interview with TV Line that episode 10 will preview his character from a time when Cas was still in part of angel battalions and not yet involved with the Winchesters. Padalecki added that this version of Cas was "before he was humanized a little bit."

Meanwhile, Mary has decided to come back to the life of hunting to be with her boys. Executive producer Andrew Dabb shared with Mashable that her return is both good and bad from Sam and Dean's point of view.

"They love that mom is out there side-by-side with them hunting, but they're also desperately worried that something is going to go wrong. And that goes for Mary too," Dabb explained.

The showrunner added that Mary will confide to Cas when it comes to things that she can't tell her boys, which makes the angel her only friend.

"So we're evolving those mother-son relationships and that friendship even more moving forward," Dabb added.

"Supernatural" season 12 airs every Thursday at 8 p.m. ET on The CW.