WARNING: The following article contains spoilers for Justice League #13 by James Tynion IV, Guillem March, Arif Prianto and Tom Napolitano, in stores now.
At the start of last summer's Justice League: No Justice, one of the DC Universe's biggest villains, Brainiac, united the world's greatest superheroes -- as well as few villains -- in order to stop the world-ending threat of the Omega Titans. However, before the Coluan could reveal his full plan to defeat the cosmic giants, Amanda Waller activated Task Force XI, a team of psychics, to hack Brainiac and find out all they could about the universe, the multiverse and everything in-between.
The psychic attack proved too great for Brainiac to counter, and Superman's villain-turned-ally died as a result, leaving the Justice League and some of their worst enemies alone to save the universe. Brainiac has been assumed dead ever since -- until now. In Justice League #13, it's revealed that Brainiac is set to return, and he might be more dangerous than ever.
Every three or four issues of Justice League, the comic switches its title to the Legion of Doom, telling a story from the point of view of the supervillain team. In Justice League #13 (aka Legion of Doom #4), we see Lex Luthor, Joker, Gorilla Grodd, Sinestro and Cheetah deal with the fallout from the events of the Drowned Earth crossover, which saw Aquaman nemesis Black Manta get kicked off the team.
With a vacancy to fill, the Legion of Doom starts a recruitment drive that, thanks to the maniacal efforts of the Joker, doesn't exactly go as planned. It's only on the final page of the issue that Lex Luthor reveals two reserve members of the Legion of Doom: Mad scientist and Amazo creator Professor Ivo, and his newest subject, Brainiac, whom the professor is meticulously putting back together.
Ivo can be seen assembling and fixing the head of Brainiac, which blew up all the way back in Justice League: No Justice #1 after Amanda Waller's Task Force XI attacked him.
Of course, it's a near sure bet Brainiac won't return as his old self. As we know, Ivo is an expert in creating dangerous robots, which means he's almost definitely making his own modifications and adding custom programming to Brainiac in order to have him answer to Lex Luthor and be, unequivocally, on the side of the Legion of Doom. If that does prove to be the case, then not only is Brainiac even more of a dangerous threat than ever, the Legion of Doom also just got a massive power upgrade.