Don seems to be the forgotten child of wizard Derk's griffin offspring. He is nearly always mentioned as part of a group of Derk's kids who are trying to help out, to warn somebody else of something, or to make things work without quite knowing how.
Don is a gold-feathered griffin, similar to Lydda and Elda, but hardly anything in the plot of Dark Lord of Derkholm is solely up to him. Young, helpful, well-intentioned -- he's a nice griffin and hopefully the future holds good things for him.