A number of interesting things are going to happen to Castiel in “Supernatural” Season 12. Watch new episodes on Thursday, 8 p.m. EST on The CW. Dean Buscher/The CW

Castiel (Misha Collins) was first introduced in CW’s “Supernatural” when he rescued Dean Winchester (Jensen Ackles) from hell. Although a lot is known about his life now, very little is known about his past. That will change when Season 12, episode 10 premieres Thursday.

Castiel was a part of a group of angels that was watching Earth. The upcoming episode will show a glimpse of what he was like when he was observing humans. “We’re seeing the earliest version of Cas to date,” Collins told TVLine while shooting the episode back in November last year, “We just came from doing a scene in an old church where we are dealing with some of Cas’ old battalion mates from heaven. It’s interesting for him to rehash old memories, for sure.”

Jared Padalecki, who plays Dean’s younger brother Sam, said that “Supernatural” fans will see what Castiel was like before he was “humanized.”

The series’ executive producer, Andrew Dabb, teased, “He [Cas] was the guy that harrowed Hell to rescue Dean Winchester. We established that, and now we’re taking a little twist on it and telling a lost story from his past that involves [guest star] Alicia Witt.”

Witt stars as Lily Sunder, a woman who has steeped herself in black magic for over a century in order to exact revenge on a band of angels that murdered her family. Her next target is Castiel.

The hunters must find a way to save Cas before Lily Sunder gets her hands on him. Of course, what the angels did to Sunder will be revealed in episode 10, titled “Lily Sunder Has Some Regrets.”

Witt is a talented actress. She recently starred in an episode of AMC’s “The Walking Dead.”

“Supernatural” Season 12, episode 10 airs Thursday, Feb. 2 at 8 p.m. EST on The CW.