Gremlin Forgemaster is an Earth-typed Epic Boss.
It was the current Epic Boss from 16 Jan 2013 to 22 Jan 2013. In that time, you could get Forgemaster's Nemesis Armor in the Dark Prince's Chest. Gremlin Forgemaster can be found in the Relic Ruins when in Heroic Mode.
It is the last Epic Boss to give Super Rare armor. It drops Blackened Leather Strips, which can be used to craft Forgemaster's Garb.