He told the other members of the Fellowship that the Die of Power had to be thrown into the Geysers of Gygax to be destroyed. After Frydo and Leegola leave, Greyfarn and the other members head to Wipe Castle to raise an army. The king had, however, sent his army to drown them. Greyfarn was later rescued by Leegola.
His name is a parody of Gandalf in Lord of the Rings.