Warning! Spoilers for Thor #6 below!
Thor has been the reluctant Herald of Galactus, following the cosmic giant crashing down on Asgard and informing him the Black Winter - a threat that could destroy the entire universe was coming. In Thor #6, the God of Thunder confronts both Galactus and the Black Winter and finds out that his future is much darker than anyone could have possibly imagined.
Thor's time as the King of Asgard was interrupted by Galactus, who informed him that he needed his help in order to save the universe from the Black Winter. Thor agreed to be his Herald, helping the Devourer of Worlds gain the energy to defeat the threat by tracking down planets with rare energies that would power him up. That's when Black Winter revealed that Galactus was actually his Herald and that he's come for him, not the universe.
In Thor #6 by Donny Cates, Nic Klein, Matt Wilson, and Joe Sabino, Galactus and the Black Winter fight, but when Thor is asked to help, he tells the Marvel villain that he's not willing to help him any further. When Galactus tries to use his powers to take down a charging Thor, the Asgardian takes the power cosmic and goes after the Black Winter. That's when Thor sentences Galactus to death and hurls Mjolnir (and an incredible blast of lightning) at him, which leaves him mummified. However, when Black Winter wants to finish Galactus off, Thor intervenes and sets off a massive bomb with the "full might of the immeasurable power cosmic..." which destroys Galactus and the Black Winter. A single snowflake left from the Black Winter falls to the ground and offers Thor the chance to see how he dies.
The future Thor sees is absolutely gnarly. Thanos wields an Infinity Stone-powered Mjolnir with a black arm. Meanwhile, he's got an army of seemingly undead Avengers joining him. In Thor's vision, the entire world around him has somehow got even worse.
The splash page with Thanos and the Infinity Hammer is a brilliant twist by Cates and Klein. Cates is no stranger to using Thanos is in his stories, but after the Black Winter/Galactus confrontation and defeat, the Mad Titan makes for a perfectly diabolical end to Thor's life. Still, there are so many questions about what comes next. Is Thanos worthy of Mjolnir? How exactly did he embed the Infinity Stones onto the enchanted hammer? What's going on with the zombie Avengers? Does his black arm have anything to do with the Black Winter? We'll find out more in future Thor stories. But for now, Cates and Klein's epic run just got even grander. Thanos. Is. Coming.
Next: MCU: How Much Odin Knew About Thanos (Could He Have Stopped Him?)