Pretty Little Liars' will soon meet Mona Monster's mother.

What Demons Are Haunting Caleb On 'Pretty Little Liars'? Tyler Blackburn's Teen Finds Unexpected Help In Rosewood

The former "A" is building up an army against her mortal enemy, and it appears the Rosewood residents will get a in depth look at the teen's family. The ABC Family drama will introduce Ms. Vanderwaal in episode 12, according to TV Line.

Named Leona, the character will be played by Sydney Penny, according to Deadline. Penny has also stared in such soaps as Days of Our Lives, All My Children, and The Bold and the Beautiful.

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In the meantime, Mona (Janel Parrish) will continue to seek revenge against the Queen of Mean.

"It'll be interesting to see how that plays out, but [Mona's] definitely building her army. We're having a lot of fun with that group and what they're plotting," explained series creator Marlene King, according to TV Line. "That definitely plays out this summer, and you'll want to watch it unfold. She has definitely assembled a group of people who were tortured by Alison and are very worried that she's coming back to Rosewood.

Find out more about the Liars when Pretty Little Liars airs Tuesdays at 8 p.m. ET on ABC Family. Click the video below to see a preview for the series' next episode, "Run, Ali, Run."