As the Eternals join the Marvel Cinematic Universe, it seems as good a time as any to look back on the history of some of the members preparing to grace the big screen. Among them, Gilgamesh is a member worth noting. Jokes have been made in trailers about the Eternals becoming Avengers, but they have joined the team in their comics history.
Gilgamesh, one of the Eternals' mightiest warriors and one of the most willing to intervene in the affairs of humanity, did become an Avenger for a time. Not too long after he left the team though, he was promptly killed.
Gilgamesh first debuted in Eternals #13 (by Jack Kirby, Mike Royer). His true name is unknown, but due to his legendary feats throughout history, he has come to be mistaken for many legendary heroes from mythology, such as Hercules or Beowulf. For a time though, Gilgamesh went by the name of the Forgotten One, in fact, it wasn't even his decision to name himself Gilgamesh. That change came later, along with a few other shifts in his personal life and ultimately, the end of it.
During an invasion of demons in New York, the Forgotten arrived in the city and assisted other heroes in rescuing Franklin Richards. Afterward, he remained, intending to work alongside Mr. Fantastic and the Invisible Woman to reform the Avengers, whose numbers had been depleted as of late. It was Reed Richards who suggested that the Forgotten One forgo his current name and adopt the codename Gilgamesh. Gilgamesh went on several adventures with the new team, battling the likes of Orphan-Maker, Growing Man, and the U-Foes. But eventually, Gilgamesh was injured while helping the Avengers battle the Lava Men and Blastaar, an extradimensional threat.
Gilgamesh was returned to Olympia, home of the Eternals, to recuperate. While he recovered, Gilgamesh elected to leave the Avengers, his essence now bound to his home. But this would later prove to be a mistake on his part. When Immortus, one of Kang the Conqueror's many alternate selves, arrived in his timeline masquerading as Kang, he kidnapped Gilgamesh. Rather than battle Gilgamesh himself though, Immortus had his underling, Neut, end Gilgamesh's life to maintain the ruse of his identity.
Fortunately, keeping an Eternal down for good is a truly difficult feat. Gilgamesh was reborn, as Eternals are wont to do thanks to the power of their Machine. But events conspired to drag him into another mess. Sprite by that point had been infuriated by his continued existence as a child and wiped the Eternals' memories of their heritage, giving them human lives. Gilgamesh was among them, now reborn as a circus strongman.
Gilgamesh would eventually be freed from Sprite's control and go on to continue his heroic career, but he never really rejoined the Avengers after that. Gilgamesh seemed more content to reestablish connections to his Eternal brethren, having been exiled from them for a time. His death and rebirth seemed to be the impetus of this change in the relationship.
Looking back, Gilgamesh actually had a good run as an Avenger. He helped stave off an invasion of demons as an audition of sorts before getting to work alongside some of the Earth's greatest heroes at a time when the Avengers were needed more than ever. And it isn't as if his time was ill-spent. Gilgamesh went up against dangerous foes and the only reason he had to leave the team was due to a severe injury. Anything that could actually force an Eternal, let alone one of Gilgamesh's power, would kill an ordinary person. So taking time to recuperate is an understandable reason to leave the team. It's just unfortunate that this also put Gilgamesh in the crosshairs of a madman.