Wishful thinking, dear Mar-Vell... As long as you are trapped in the dreaded negative zone! And though you cannot hear me... Rest assured that there you shall STAY... FOREVER! Thus swears your arch-enemy... YON-ROGG!
~ Yon-Rogg taunting Mar-Vell.
Yon-Rogg is a minor antagonist in the Marvel universe, a colonel of the Kree empire's army introduced as an antagonist of the first Captain Marvel (Mar-Vell)
He hated Mar-Vell because of his fear of being outranked by him due to his accomplishments in the Kree military, and also because of his love for the medic Una.
Yon-Rogg is the commander of the Helion, a Kree spaceship that was sent to Earth by the Supreme Intelligence. Yon-Rogg had a deep hatred towards Mar-Vell due to his love for the Kree medic Una. He ends up leaving Mar-Vell on Earth so that Una can be his. Yon-Rogg later unleashes the Sentry 459 to dispose of Mar-Vell. During his fight with the Sentry, Mar-Vell learned that the Sentry attacking him was sent by Yon-Rogg. After Mar-Vell defeats the Kree Sentry, Yon-Rogg contacts Ronan The Accuser to pass judgement on Mar-Vell's actions. Ronan declines the offer stating that the mission was not jeopardized by Mar-Vell's actions.
When Mar-Vell starts to develop a friendship with Carol Danvers, Ronan the Accuser orders Yon-Rogg to lead some Kree soldiers into executing Mar-Vell. Yon-Rogg is happy to oblige. After Una dies from her injures upon being caught in the crossfire between the Kree and the Aakons, Zo frees Mar-Vell from the control bands that Yon-Rogg and has Mar-Vell go after Yon-Rogg for revenge upon bestowing new powers onto him. Mar-Vell uses his illusion casting to taunt Yon-Rogg into thinking that he is alive. While a supply ship is restocking the Kree ship, Mar-Vell ends having a brief fight with Yon-Rogg before returning to Earth to save Carol Danvers from Man-Slayer.
Mar-Vell meets Rick Jones, the honorary member of the Avengers, who tries on Mar-Vell's Nega Bands which he uses to have a brief fight with Yon-Rogg. Yon-Rogg manages to escape afterwards. Yon-Rogg begins his next plot against Mar-Vell. When Yon-Rogg captures Carol Danvers and Mar-Vell catches up to him, Yon-Rogg uses a Psyche-Magnetron to create a Kree super soldier to help him fight Mar-Vell. During the fight, Carol Danvers is injured and the Psyche-Magnetron is damaged with some of its energies irradiating Carol Danvers. After Mar-Vell destroys the Kree Mandroid, Yon-Rogg is seemingly killed when the Psyche-Magnetron explodes. This battle led to Carol Danvers being exposed to the damaged Psyche-Magnetron's energies which would lead to her becoming Ms. Marvel and the current Captain Marvel.
Yon-Rogg is later revealed to have survived the Psyche-Magnitron's explosion, gaining a telepathic link with Carol Danvers' via a shard of the Magnetron that is lodged in her brain (which is also causing a brain-damaging lesion in Carol's head). After stealing the remains of the Psyche-Magnetron from Carol, Yon-Rogg tries to give it to the Kree Empire only to be turned down. He then takes the name "Magnetron" and uses Carol's memories and its power to recreate enemies from her past before attempting to drop a Kree city on top of New York City. Carol is able to destroy the telepathic link and Yon-Rogg's powers by aggravating the lesion in her head until it bursts, though at the cost of all her memories. The depowered Yon-Rogg was taken away by Captain America.
In Other media
Avengers: Earth's Mightiest Heroes
Yon-Rogg appears in the animated series Avengers: Earth's Mightiest Heroes. He sends a Kree Sentry and Mar-Vell to Earth to determine if its worthy of being part of the Kree empire. After the Hulk damages the Sentry, which activates its self-destruct sequence, an hologram of Yon-Rogg appears. Mar-Vell pleads for Yon-Rogg to call of the Sentry but Yon-Rogg refuses and brands Mar-Vell a traitor. In the episode "Welcome to the Kree Empire", Yon-Rogg accompanies Mar-Vell, Ronan the Accuser, and Kalum Lo to Earth in order to get Earth to surrender to the Kree Empire. The Kree taking part in the attack on Earth are defeated by the Avengers and and are remanded to Prison 42.