'Supernatural season 12 episode 10 spoilers: Someone from Castiel's past arrives; Alicia Witt speaks on Lily's history with Castiel

Someone from Castiel's past comes back to get revenge on the upcoming episode of The CW's long-running series "Supernatural" season 12.
Titled "Lily Sunder Has Some Regrets," tonight's episode will introduce a new female character. According to the official synopsis, Lily Sunder (guest star Alicia Witt) enters the picture and steeps herself in black magic. She develops her powers for over a century in an effort to exact revenge on a group of angels who is responsible for murdering her family. Sam (Jared Padalecki) and Dean (Jensen Ackles) must race against the clock and take action to keep Castiel (Misha Collins) from becoming her next victim.
Considering how long Castiel has been around, "Supernatural" fans know that a lot of people and angels have come into contact with him over the years. This week, however, someone from his past is returning, and it won't necessarily be a happy reunion. Witt recently caught up with Entertainment Weekly, and she revealed that Lily has a bad history with Castiel.
"She has been around for a very long time and is determined to rectify things," Witt said, adding that her character is in town because she wants to "get even for something" or "settle the score." Moreover, the actress promised that fans are going to understand why Lily is furious at Castiel. "You do get to see what happened and you get to see Lily, my character, back in the day," she continued. Witt also teased action-packed scenes with her character and Castiel, saying that there'll be "a lot of angel blade fighting."
Before being with Sam and Dean, Castiel was once a part of a group of angels tasked to watch over Earth. Episode 12 will give viewers a glimpse of what he was like when he was just observing how humans live.
"We're seeing the earliest version of Cas to date," Collins told TVLine in November when he was shooting the episode. "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," he added.
The 12th season of "Supernatural" airs every Thursday night at 8 p.m. ET on The CW.