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General Grugger was the leader of a group of Gaztak mercenaries.
Grugger, his aide Brotadac, and his marauding band were hired by Meglos to bring an Earthling to Zolfa-Thura. Once there, Meglos made a deal with Grugger, promising him power in return for the Tigellans' Dodecahedron.
Grugger took him to Tigella to steal the Dodecahedron from their underground city. Grugger and his party stayed with their ship. They captured Romana II and forced her to take them to the TARDIS. Instead, she led them in a circle before initiating a Bell Plant attack upon them. Grugger eventually broke free from the plant, as did his party. They then attacked the Tigellan city and managed to beat back the defenders.
Together with Meglos, Grugger and his band left for Zolfa-Thura. Once there, they set up the Dodecahedron so that it could fire a powerful blast. Grugger requested that Tigella be that target, angry over the loss of life sustained by his crew there. However, the Fourth Doctor reverted the controls so that Zolfa-Thura was destroyed, along with Grugger.