Maximus, an Inhuman, was the second son of two of Attilan's top geneticists, Agon, the head of the ruling Council of Geneticists, and Rynda, director of the Prenatal Care Center. Subjected to the DNA-altering Terrigen Mist while still in his mother's womb, Rynda's powers allowed her to filter the Terrigen that entered Maximus' body. On Agon's guidance, she ensured the Terrigen concentrated on the baby's brain to grant him a heightened cognitive function, and also made it more pure, and thus closer to the Primagen of legend.
Maximus' gift manifested in the form of increased intelligence and mental control, powers his parents determined were attuned to those of his elder brother Black Bolt, and vice versa. Maximus' powers additionally caused him to experience flashes of future memories. As he matured, Maximus hid his developing psionic powers from the community but was less successful at disguising his antisocial tendencies. When he was about sixteen, Black Bolt was released from the protective chamber in which he had been confined since birth due to the destructive nature of his Terrigen mutation. One of Maximus' first ploys was an unsuccessful attempt to force his brother to unleash his highly destructive vocal powers in order to have him reincarcerated.
A month later, Black Bolt witnessed Maximus making a treacherous pact with an emissary of the Kree, the alien race responsible for genetically accelerating the Inhumans eons before. In addition to his objective of seizing the throne, Maximus was making a pact with the Kree in an attempt to learn more about the legendary Primagen, with which he had become obsessed in discovering. In an attempt to stop the fleeing emissary so that he could be questioned by the ruling council, Black Bolt used his forbidden power of the quasi-sonic scream and blasted the alien ship out of the sky. When the ship crashed to earth, it landed on the parliament building, killing several key members of the Genetics Council, including the boys' parents. The reverberations of Black Bolt's voice also affected Maximus, who was standing nearby. Maximus' powers were expanded, allowing him to catch a small glimpse of every moment of his life all at once, driving him mad. The reaction also supressed his nascent mental powers once it was over. After the Forgotten Reign, Black Bolt assumed the throne and Maximus vowed to oppose his brother and eventually usurp his rule.