Reign, the big bad on “Supergirl” this season, is a monster and a mom. Odette Annable is playing this fascinating character to the max.

At the close of season 2, viewers learned that another pod escaped Krypton’s destruction, containing a bio-engineered weapon, a Worldkiller named Reign. In the DC comics, the Worldkillers are bloodthirsty, super-powered beings that set out to conquer Earth. But when Annable makes her debut as the character in the season premiere, she is a single mother named Samantha who has no idea about her true identity.

For the first seven episodes, Kara and her friends got to know Samantha and her young daughter. Ordinary, likeable people. Then, in episode 8 (“Wake Up”), Reign emerges. Unlike other super villains, we watch the big bad become the big bad.

Sam’s personality is not completely wiped out as she turns into Reign. The mother is still there, but increasingly confused about what’s happening and why she’s sharing her body with a Kryptonian vigilante.

Annable told EW:

Samantha is a single mother, she’s a hard worker, she’s very much a working mom in the sense that she’s trying to juggle it all, as one does, as I do in real life. She loves her daughter more than words can express. They have a really special bond. What I think is really special about this storyline is it’s a slow play and you’ll get to see this whole heartbreaking story unfold in a really — they’re taking their time with it, and we have the time to do it. I think the audience is really going to hopefully relate.

In this week’s fall finale, Reign is in full force, taking on Supergirl in a spectacular battle… which ends with the shocking sight of a physically brutalized Kara, dropped off a roof and sent into a coma.

We wait until next year to see what happens next.