The Mad Titan is returning to his old ways, and to do that he requires a throne. Unfortunately one of his disciples has used his absence to take the throne for himself, but that altercation is small change compared to the other big reveal in Thanos #1.
Big spoilers from here on out, so be warned.
Thanos returns to the Black Quadrant to find his former cohort Corvus Glaive sitting on the throne. It's evident why this would anger Thanos, as typically people like Glaive wold have merely held station until he returned. Glaive has completely usurped the throne, and though you wouldn't think it, he's proven to be a rather fair and efficient ruler.
Progress isn't something that matters to someone like Thanos though, and it doesn't take him long to dispel of Glaive's forces and even Glaive himself. Thanos crushes his staff and offers him mercy, though it should be noted that "mercy" involves taking his own life, as what Thanos will do to him is much, much worse.
The death of Glaive is a surprising one, but it isn't the key moment. No, that comes at the very end, but some context first.
Thanos's family lineage is rather fractured, to the point that, well, it's safe to say Thanksgiving is just a complete downer. His son, Thane, is assembling a group of tasked with one sole goal, which is to take the Mad Titan down. So far it includes Tryco Slatterus and Star Fox, but Thane is also getting help from Death herself, who has quite the complicated history with Thanos.
When Thane is doubting whether his ragtag group can actually defeat Thanos, Death reveals a key fact that should slide things into their favor.
It turns out Thanos is dying, and regardless of how powerful he is, you can only hold off death for so long. How or why it's happening has not been revealed, but it is interesting to see Marvel go this route when Thanos will be the main villain in the upcoming Avengers: Infinity War. While the comics and films are succinctly different in many ways, having Thanos not be among the living would leave a large void.
You can see the big reveal in the gallery.
Thanos is written by Jeff Lemire with art from Mike Deodato. It also includes colorist Frank Martin and Letterer Clayton Cowles (VC). Thanos #1 is in stores now.
NEXT: EXCLUSIVE: Marvel Announces New Thanos Series / EXCLUSIVE: Thanos #1 Marvel Preview / Marvel Releases Doctor Strange Vs Thanos Promo / Mad Titan's World: 10 Most Memorable Thanos Moments / 5 Essential Thanos Stories