Go the the Ishe Inn and talk to Mahar. Listen to his story, and then tell him you are interested in helping. He will ask for Bubu Worms to make some medicine. Go to the Glass Desert and fight Basilisk, Tyrannoses, and Kid Dragons until they drop some Bubu Worms (about 10% chance). Return to Mahar and give him the worm to measure. Your reward depends on the length: