Blok is a native of the planet Dryad, whose native species is one of the few silicon-based life forms. Dryad was destroyed by a series of natural disasters, during which the Legion of Super-Heroes aided in the evacuation. A group of children from the planet were taken at the same time by the Dark Man and told that the Legion was responsible for the destruction of their planet; Blok was among this group.

Given powers by the Dark Man, the group attacked the Legion as the League of Super-Assassins. Blok overcame the conditioning of the Dark Man and was captured by Polar Boy. He later helped to defeat the Dark Man in battle. He applied for and was given Legion membership.

Blok is incredibly strong and invulnerable, but not very agile so he typically depends on his invulnerability to protect him in a battle. Due to his great weight, Blok requires three Legion Flight Rings to fly.