This article contains spoilers for the Supergirl season 2 finale.
At the end of Supergirl season 2, we saw another baby leaving Krypton the day it exploded. She was sent to Earth, with a view to "reign", by a group of shifty-looking scientists.
Fans quickly worked out that this new addition to the show would grow up to be Reign, a biological weapon from the comics.
Reign's comic book backstory - Kryptonian scientists create her as a super-powerful 'Worldkiller', then send her out into the galaxy without any real instructions - looks set to be recreated on screen.
And now we know who will be playing the adult version of Reign in Supergirl season 3: Odette Annable, who you might recognise from Cloverfield, Banshee or House MD, has nabbed the role.
"Greg [Berlanti] and I have wanted to work with Odette for years," said executive producer Andrew Kreisberg. "We are beyond excited to have her join our cast in the scary, powerful and heartbreaking role of Reign."
Supergirl season 3 Reign
In the comics, Reign arrived on on Earth some time after Kara Zor-El, after realising that Krypton - and her creators - were no more.
Reign rampaged through New York, and tried to convince the Maiden of Might to join her in taking over the planet. That offer, as you'd expect, didn't go down too well. It has also been teased that Reign isn't the only Worldkiller in existence.
We're excited to see how this arc will be adapted for the small screen, and what the chemistry between Odette Annable and Melissa Benoist will be like.
Supergirl season 3 release date
The exact date hasn't been set yet, but we know that about Supergirl season 3 will arrive on The CW/Sky 1 in autumn 2017.
We'll keep you posted as we hear more.