Mark Grayson, known as Invincible, is the protagonist of the series 'Invincible.' He is a teenager who inherits superpowers from his father, Omni-Man, a powerful alien from the Viltrumite race. As Invincible, Mark struggles to balance his high school life, relationships, and heroic responsibilities. Throughout the series, he faces numerous villains, learns about his heritage, and grapples with the complex morality of being a superhero. Mark's journey is a coming-of-age story that explores themes of identity, responsibility, and the legacy of power.