Gruber was a German scientist during World War II.
Gruber was part of a group of Nazis, led by Luther, who took over the village of Pax Lucis. They erected a barrier around the village using a captured lightwanderer. Gruber was in charge of the machine that would destroy all of England.
Gruber was sure that the machine would destroy the entire world. This did not upset him, however, as he was obsessed. Gruber was killed with the rest of the Nazis when the lightwanderer was freed. (PROSE: Special Weapons)