'Supergirl': Who Dies in the Season 3 Finale?

The stakes were high for Supergirl tonight in its Season 3 finale with the Kryptonian witches and Reign making a play to devastate the Earth for their own dire purposes. However, even with the show set to return next fall giving fans hope that the Girl of Steel would prevail, tonight's episode marked the end for some of The CW series' characters.

Spoilers for tonight's Season 3 finale of Supergirl, "Battles Lost and Won".

While the deaths in tonight's episode weren't entirely unexpected, they were still emotional for fans of the series -- especially when it came to the passing of M'yrnn J'onzz (Carl Lumbly). The death of J'onn's (David Harewood) father is one that fans had been bracing themselves for since the show returned from midseason hiatus. It was revealed that M'yrnn had a form of Martian dementia and as the season worked its way towards a final showdown with Reign it also saw M'yrnn's condition worsen. Last week, M'yrnn asked his son to participate in a Martian traditional ceremony that would allow him to transfer his mind and knowledge as well as bring an end to his life.

J'onn reluctantly agreed last week, but the ritual was cut short when the danger posed to Earth by the Kryptonian witches and Reign reached critical mass. Both J'onn and M'yrnn showed up to help save the world. However, death can only be delayed so long and tonight, M'yrnn succumbed, but not simply from his illness. Instead, M'yrnn sacrificed himself to stop the Earth from being torn apart but not before giving J'onn one final, very important memory: the dawn of his species very existence.

Of course, the emotional death of M'yrnn wasn't the only passing in tonight's episode. Several people close to Supergirl died but there was a major twist. After successfully gaining her strength from the Fountain of Lilith, Sam awoke with super powers and joined the heroes in taking on Reign in the Fortress of Sanctuary. However, when Sam shows up to kill Reign it goes horribly awry. After being tossed into the flames of the cauldron, Reign's laser vision goes fires uncontrollably, taking down Alura (Erica Durance), Mon-El (Chris Wood), and Sam. Reign may have been killed, but so did those who Supergirl loved.

Devastated and realizing that she could have found a better way to stop Reign, Supergirl takes Mon-El's Legion ring, hits a disruption in time, and goes back to the moment Sam showed up at the Fortress. Instead of killing Reign and triggering everyone's deaths, she instead uses the harunel to send herself, Sam, and Reign into the Valley of Juru where Sam is able to defeat Reign once and for all without the shocking body count -- and with Sam finally free of her dark alter ego.

As for what those deaths will mean in the long run, that is anyone's guess though the episode did see J'onn step down from the DEO following the death of his father and with Sam left human following the defeat of Reign, her days of adventure are likely over. Fortunately, fans will get to see how things play out when Supergirl returns for its fourth season on Sundays this fall.

What did you think about tonight's season finale? Let us know in comments!