The Revengencers
The Revengencers is an anti-Dethklok terrorist group formed by Edgar Jomfru and the Metal Masked Assassin in an attempt to exact revenge against Dethklok for the pain they have caused them (both their younger brothers were killed by Dethklok's minions). Though the organization was seeming destroyed at the end of the second season, the Revengencers reappear in season four.
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