Grumb was formerly a soldier in the Nameless Army when he was drafted into the Green Lantern Corps, and for the first few months of his life as a Green Lantern he never had a name. He adopted the name "Grumb" and has focused his goals on one day working as a training instructor alongside Kilowog.  Grumb was a member of the Corps unit sent to Coast City to provide support for Earth Lanterns Hal Jordan and Kyle Rayner during the Sinestro Corps War.