Mason Eckhart is the leader of the GSA and the prime antagonist of Mutant X in Season 1. He is portrayed by Tom McCamus.
Eckhart forcibly recruits Brennan Mulwray to his cause and, after capturing the telepath Ruby, obtains the location of the Mutant X safehouse. Eckhart orders a raid and succeeds in capturing all the mutants present except for Jesse Kilmartin, who manages to escape and organize a rescue against the GSA.
Eckhart hires Sonya and Yuri to use a secret Russian weapon developed by the KGB to hunt down rogue mutants.