Warning: SPOILERS for Infinity Wars: Prime #1

Marvel's biggest comic event of the year Infinity Wars has kicked off with the shocking death of Thanos. The Mad Titan's death comes at the hands of a new character named Requiem. The decision to kill off Thanos is surprising to say the least, considering how important the character is to the Marvel Cinematic Universe.

Of all the characters packed into Avengers: Infinity War, it was Josh Brolin's Thanos who received the most screen time. Having been teased since Thor, Thanos finally emerged to become the MCU's greatest threat to date. As the MCU's "biggest and baddest" villain, only Thanos could pull off a victory over the combined forces of the Avengers, the Guardians of the Galaxy, Doctor Strange, Black Panther, and Spider-Man.

The Mad Titan will be around for at least one more movie in Avengers 4 - but the same can't be said for his comic book counterpart.

Related: Thanos 'Dies' in His Final Comic Book Story

In Infinity Wars: Prime #1, Adam Warlock and Doctor Strange investigate Soulworld and discuss what to do about the Infinity Stones. Adam Warlock leaves Strange with an ominous warning that Thanos will come looking for them. Meanwhile, Thanos is visited by a masked figure who goes by the name "Requiem."

Just as Thanos is planning to begin his conquest, Requiem surprises Thanos by stabbing him in the back and lopping off his head with a sword. As the Mad Titan takes his final breath, Thanos feels that he has died a "fine death."

The ending of Infinity Countdown, the series that served as a prelude to Infinity Wars, made it appear that Thanos was to about to mirror his MCU counterpart by becoming the Marvel Universe's next major adversary. He was believed to be the threat that Doctor Strange was preparing for when he tried to assemble a new Infinity Watch.

The popularity of the MCU's Thanos only magnifies the significance of the character's death, and makes it even more unexpected. As Thanos is currently one of Marvel's biggest characters, many would have expected the Mad Titan to be the "big bad" of Infinity Wars, which is definitely going to be seen by comic fans as Marvel Comics' answer to Avengers: Infinity War. The events of this issue make it abundantly clear that this is not the case... and throws the future of the story into total disarray.

The introduction of Requiem is sure to have massive repercussions for the Marvel Universe as a whole. Killing Thanos is more than enough to gain a reputation as a force to be reckoned with.

Infinity Wars: Prime #1 is on sale now from Marvel.

More: Joss Whedon Was Unsure Of Thanos' Story After Avengers