_Supergirl_: Everything You Need to Know About Season 3

Supergirl closed out Season 2 with heartbreak as Kara (Melissa Benoist) was forced to say goodbye to her boyfriend Mon-El (Chris Wood) for an undetermined amount of time. With her love lost somewhere in space, the new season finds her coping with his absence back on Earth while also dealing with a slew of new villains that have arrived in National City.

There's a lot going on so if you find yourself blanking on some of the details, don't worry. We've got you covered! Ahead of the premiere, we broke down everything you need to know about Season 3.

Kara's mom won't be the same.

Kara's deceased mom Alura will continue to impart her much-needed wisdom via artificial intelligence, but her holographic form will look slightly different. That's because Eric Durance, who played Lois Lane opposite Tom Welling's Clark Kent in Smallville, is replacing Laura Benanti in the role. Benanti had to back out this season due to other work commitments.

The show has already seen a shakeup behind-the-scenes.

Producers Jessica Queller (who also worked on Gilmore Girls and Gossip Girl) and Robert Rovner (who executive produced Private Practice) have been promoted to co-showrunners alongside Andrew Kreisberg. Kreisberg previously shared those duties with Ali Adler, but the latter stepped down earlier this year and remains a consultant on the series.

There will be multiple villains.

This season will see a number of new baddies including Robert DuBois aka Bloodsport, an ex-military soldier who uses stolen tech from his old base to hide a nuclear weapon. Plus, Heroesand Agents of S.H.I.E.L.D. alum Adrian Pasdar steps in as ruthless real estate developer Morgan Edge whose big plans for National City don't sit well with Kara and Lena Luthor (Katie McGrath).

Yael Grobglas is set to play Psi, a villain with psychic abilities who has a surprising inpact on Supergirl.

But Reign will be the big bad.

Odette Annable (Astronaut Wives Club) joins the show as Reign, the leader of a group of genetically modified aliens known as Worldkillers who have an insatiable thirst for destruction. Annable's character briefly appeared in the Season 2 finale as the baby in the pod who also made it off Krypton before the planet exploded. With no memory of her past, the single mom who goes by the name Samantha will seek out Supergirl to find out more about her heritage.

Supergirl is getting a Tremblay.

No, not Jacob. His sister Emma heads to the series as Ruby, a young girl obsessed with the Girl of Steel who also keeps getting into trouble.

J'onn J'onnz isn't the last (Green) Martian alive, after all.

The new season will be a family affair for J'onn J'onnz (David Harewood), whose father is headed to town. Carl Lumbly is set to appear as M'yrnn and he believes his son has "gone so Earth-man," according to showrunner Andrew Kreisberg.

You're going to see a lot less of Maggie.

Maggie may have gotten engaged to Alex Danvers (Chyler Leigh) in the Season 2 finale but she won't be around as much in the new season. Floriana Lima, who plays her, has decided to pursue other opportunities and will now be a recurring character. It's unclear what that means for her relationship with Alex and whether or not they'll actually make it down the aisle. On the plus side, it doesn't look like she's going to be killed off anytime soon.

And probably Mon-El, too.

When we last caught up with the reformed Daxamite, he was forced to leave Earth after Kara set off a nuclear weapon which made the planet's atmosphere toxic to him (but saved everyone else from his evil mom Rhea, played by Teri Hatcher). Unfortunately, his pod was knocked off course and fell through a portal to another dimension. If and how he makes his way back to Kara remains a mystery.

There's another four-part crossover headed your way.

Yep, Supergirl is teaming up with the spandex heroes from Arrow, The Flash and DC's Legends of Tomorrow for another super-sized crossover event. This year's four-part spectacle takes place Monday, Nov. 27 and Tuesday, Nov. 28 starting at 8/7c on the CW. The special will be called "Crisis on Earth-X" and center around Barry (Grant Gustin) and Iris's (Candice Patton) upcoming nuptials.

Supergirl kicks off the CW-DC season on Monday, Oct. 9 at 8/7c.

(Full disclosure: TV Guide is owned by CBS, one of the CW's parent companies.)