This page contains major spoilers, you have been warned!
Skull Mask is one of the four leaders of the biggest groups in the Outsiders.
Skull Mask was a member of a glory Civilization which was destroyed by the Dragon of Destruction, Napolitioan.
Although he cooperated with the Outsiders, Skull Mask pursued his own goals. He wanted to repair the Artemis system in order to restore the dead Empire by building his own functional operational facility. Skull mask also used the Artemis functions to manipulate causality to create powerful homunculi which were capable of near-infinite regenerations and even minor time-bending powers.