SPOILER WARNING: The following article contains spoilers for Injustice vs. Masters of the Universe #3 by Tim Seeley, Freddie E. Williams II, Jeremy Colwell and Wes Abbott, on sale now.
When Injustice 2 was announced, fans were excited to learn Superman's cousin, Supergirl, would be added to the game. From a storytelling standpoint, another Kryptonian witnessing Superman becoming like Zod set up an intriguing conflict, particularly considering that although she did initially side with Kal-El, Kara Zor-El was ignorant of the monster the Man of Steel had truly become.
As the comic tie-ins from DC have mapped out more of her mentorship under Wonder Woman and prepared her for when she'd eventually meet her cousin, we've seen the good in her. She'd eventually switch to Batman's Resistance and stand on the side of liberty and justice, but there is no happy ending for her. With the He-Man/Injustice crossover spinning out of Superman's victorious video game ending, Supergirl's final fate has now been revealed, and it's as cruel and dark as you'd expect.
Kara did try to reason with her cousin as she saw the good in him and wanted him to be the beacon of hope they all knew he could be. Even Bruce harbored a glimmer of faith Superman would see the light in her and renounce his evil ways. But Superman selfishly wanted the warrior that trained under Wonder Woman and Black Adam to be his successor and help lead his dictatorship, even trying to use Brainiac's invasion and enslavement of Kandor City to keep her on his team. Despite all that, she honored what the House of El stood for and rebelled against Kal-El. Sadly, when he won, he bonded with Brainiac's technology and turned Batman into the Black Oracle, a slave to help him control crime and rule Earth.
Come this crossover, we're now seeing Damian Wayne as the new Batman, trying to fill in and lead the Resistance against Superman's new world order and rescue his father. However, it's no easy feat because Wonder Woman is a vengeful general, even ready to kill kids, and ThoughtCrime has the world in shackles, cowering in fear, making Damian's job all the more tough.
This led to him recruiting Prince Adam of Eternia for the cause, but as we witnessed the upgraded rosters of both sides of the war unfolding, Supergirl was nowhere to be found. The video game's ending had Superman trapping her in a cell under a red sun, negating her powers, and threatening her to join his team. so we assumed she was being kept prisoner somewhere. Well, now it's revealed she turned down his offer, as expected, but instead of being held under the red sun, she's been sent to the one place she fears most: The Phantom Zone.
Every Kryptonian knows this is a living hell, so for Superman to send her there, it's clear he has little to no love for her anymore. He did divulge to her in the game that he was already bringing cities like Kandor and its sister city, Argo City, back to life, and trying to do the same for alien species such as Daxamites and Czarnians (Lobo's people), so it seems she still didn't want to take part in anything which would shape him as the overlord and savior of these worlds. Kara was also repulsed at seeing what he did to Batman, so hopefully we soon find out how she's faring in the Phantom Zone after sticking up for her new mentor.
Wonder Woman seems to enjoy Supergirl's exile, which makes sense because she's probably the only person who can kill her, apart from Superman, so it's only fitting such a big threat be hidden away.
Still, you can't help but feel that the Resistance does have plans, not just to rescue Bruce Wayne from Superman's clutches, but also to extract Kara and level the playing field. Until that time comes, one can only hope she's alive and well amongst the ghouls that haunt there because we all know the Phantom Zone is indeed a nightmarish non-death sentence.