Maximus

Maximus, also known as Maximus the Mad, is an Inhuman and brother of the Inhumans' rightful king Black Bolt.

After Black Bolt left the Great Refuge in order to search for Medusa, Maximus became king, and ruled the city. After branding leaving the Great Refuge as an act of treason, Maximus attempted to have the citizens of the Great Refuge kill Black Bolt and his family before The Fantastic Four saved them. He tried to use the Terrigen Mists to kill normal humans, but it failed since, as highlighted by Mister Fantastic, humans and Inhumans are more similar than different. Maximus then created the negative barrier in order to trap all Inhumans inside it.

During the time the Inhumans were trapped inside the Great Refuge by the negative barrier, Maximus reverted to an almost childish state of mind, though at the same time he kept inventing some devices. During this time one of the few good things he did was to create a special harness that allowed Triton to breathe air. Black Bolt eventually destroyed the barrier.