Get the egg from the beach on the north west side of the island, and give it to the harpy queen.
Kill the dragon and give the corpse to the harpy queen.
Leper Cure Quest
Find Ranthal in the Aalen Forest and talk to him (say "mushroom"). He will give you a mushroom that you can bring to the old leper on the island of Polyargos, who believes that it helps to cure their illness.
Kill the harpies and give their corpses to the old leper, he will pay you 50 gold for each.