After the Brood-infected officer Devros threatened Kree interests, Mar-Vell was reassigned with Una and Yon-Rogg aboard the vessel Helion for a mission connected to Earth. The recent reactivation of Kree Sentry #459 by the Fantastic Four renewed interest in humanity and led the Supreme Intelligence to dispatch Mar-Vell to investigate the planet.

During his arrival, Mar-Vell witnessed the death of scientist Walter Lawson and adopted the man’s identity to better study humanity. At Cape Canaveral he encountered security chief Carol Danvers, beginning one of the most important relationships in Marvel history. Though Carol developed feelings for him, Mar-Vell remained devoted to Una.

Yon-Rogg attempted repeatedly to eliminate Mar-Vell by manipulating Sentry #459 and orchestrating increasingly dangerous situations. Mar-Vell repeatedly defeated these threats and gradually abandoned his original mission. Humanity impressed him. Earth ceased being a target and became something worth protecting. During these early adventures, onlookers misheard his name and began calling him “Captain Marvel,” establishing the identity he would forever carry.

Tragedy soon followed when Una died during conflict involving the Aakon. The loss deeply affected Mar-Vell and permanently damaged any remaining loyalty he held toward the Kree hierarchy.

Mar-Vell later became entangled in political conspiracies led by Ronan the Accuser and Zarek. They granted him enhanced abilities and attempted to frame him as the destroyer of Hala in a plot intended to overthrow the Supreme Intelligence. Mar-Vell defeated their plans, saved the Supremor from assassination, and was rewarded by retaining many of the powers they had given him.

Shortly afterward Mar-Vell became trapped within the Negative Zone. From there he forged a psychic connection with Rick Jones through the Nega-Bands. By striking the bands together, Rick and Mar-Vell exchanged places between dimensions. The partnership became one of Marvel’s most unusual heroic bonds.

Mar-Vell’s rivalry with Yon-Rogg ended during the Psyche-Magnetron incident. While attempting to save Carol Danvers, Mar-Vell allowed Yon-Rogg to perish. Unknown to everyone present, energy from the device altered Carol’s genetic structure using Mar-Vell as a template, eventually leading to the creation of Ms. Marvel and later Captain Marvel (VII).

The Kree-Skrull War elevated Mar-Vell from hero to galactic figure. Serving as one of Earth’s principal defenders, he fought alongside the Avengers while Rick Jones unknowingly unleashed latent psychic abilities manipulated by the Supreme Intelligence. The experience ultimately exposed the Supremor’s plans and contributed to Mar-Vell’s final break with the Kree Empire.

Scientific experiments performed by Professor Benjamin Savannah altered Mar-Vell further, granting him photonic energy projection. Although immensely powerful, these abilities fluctuated depending on available solar energy.

When Thanos sought the Cosmic Cube to impress Death, Mar-Vell was approached by Eon. Judged worthy, Mar-Vell received Cosmic Awareness and the mantle of Protector of the Universe. This transformation elevated him beyond ordinary heroism and gave him insight into events on a universal scale. Guided by Cosmic Awareness, Mar-Vell discovered the Cosmic Cube remained Thanos’ power source and shattered it, defeating the Titan in one of the greatest victories of his life.

Mar-Vell later battled Nitro during an incident involving stolen nerve gas. Though victorious, he was exposed to carcinogenic compounds. The effects appeared harmless at first but would later prove fatal.

Mar-Vell next opposed the Lunatic Legion, turned permanently against the Supreme Intelligence, battled the Stranger, Cheetah, Drax the Destroyer, and numerous cosmic threats. During a clash involving the Super-Adaptoid, Rick Jones was finally separated permanently from the Negative Zone cycle that had defined much of Mar-Vell’s career.

His genetics later made him the target of Dr. Minerva, who attempted to force reproduction in hopes of creating a superior Kree lineage. Mar-Vell rejected the plan and saved Rick once again.

While aiding Titan against the corrupted systems of ISAAC, Mar-Vell fell in love with Elysius. Their relationship became one of the happiest periods of his life. He later returned to Earth and helped oppose Michael Korvac alongside the Avengers.

Eventually Mar-Vell learned the truth: his exposure to Nitro’s nerve gas had caused terminal cancer. Even the advanced sciences of Titan, the Kree Empire, and Earth could not save him. Heroes and former enemies gathered at his bedside as he died. The Skrulls honored him with the Royal Skrull Medal of Valor, a nearly unprecedented act toward a Kree warrior. He was granted honorary Avengers membership and passed peacefully while experiencing one final vision of battle alongside Thanos. Mar-Vell died on Titan, one of the few major heroes in Marvel history whose death remained meaningful for decades.

Mar-Vell’s legacy continued after death. Elysius used his genetic material to create Genis-Vell and later Phyla-Vell. Carol Danvers carried part of his power. Quasar inherited the Protector role. Multiple heroes adopted the Captain Marvel identity, yet Mar-Vell remained the standard by which all successors were judged. His spirit appeared repeatedly to allies and descendants, while even his remains influenced future conflicts involving the Nega-Bands and the Nega-Bomb.

• Psyche-Magnetron incident creates path for Ms. Marvel (Captain Marvel #18, 1969)
• Kree-Skrull War (Avengers #89–97, 1971–1972)
• Receives Cosmic Awareness (Captain Marvel #29–33, 1973)
• Defeats Thanos and destroys Cosmic Cube (Captain Marvel #33, 1974)
• Nitro encounter and cancer exposure (Captain Marvel #34, 1974)
• Lunatic Legion conflict (Captain Marvel #47–50, 1977)
• Separation from Rick Jones (Marvel Two-in-One #52, 1979)
• Relationship with Elysius (Captain Marvel #58–62, 1979)
• Korvac conflict (Avengers #167–177, 1978)
• Death of Captain Marvel (Marvel Graphic Novel #1, 1982)
• Legacy through Genis-Vell (Silver Surfer Vol. 3 #6, 1988)
• Legacy through Phyla-Vell (Captain Marvel Vol. 4 #16, 2003)