Captain Mar-Vell is a member of the Kree, the alien humanoid race which has built an empire throughout the galaxy known as the Greater Magellanic Cloud. After battling the Skrulls on Earth, Mar-Vell finds himself trapped in the Negative Zone, only able to return to this universe when Rick Jones exchanges places with him via cosmic nega-bands.
Mar-Vell joins the heroes and gods battling Thanos and his plans for destroying all life in the universe. During the battle, the extraterrestrial being called Eon grants Mar-Vell a psionic ability called "Cosmic Awareness", and designates him as "Protector of the Universe". Captain Mar-Vell joins forces with Drax the Destroyer in bringing about Thanos's defeat.
Next Mar-Vell battles Nitro, who had stolen a powerful nerve gas. A canister of the gas breaks open, but Mar-Vell uses his powers to seal it. The gas causes Mar-Vell to collapse, but he seems to recover fully afterwards. However, the gas was also carcinogenic, and finally the cancer takes its toll. Mar-Vell spends his last days on Titan where the hero dies, surrounded by his lover, Elysius of Titan, Jones, the Avengers, and various other friends.
