"An Odd-smelling flower, though very pretty."
With Durlyle, you should be polite and romantic to gain his help (if you're impolite to him when receiving the cloak quest, you won't have the opportunity to receive the Belladonna Flower quest when returning the cloak). He wants you to retrieve a cloak. Head to Dradeel's hut in Isle of Balduran [North]. When you return you can insist on payment for the cloak if you cherish an extra 10gp but he will not help you later! Otherwise return the cloak for some tales. Talk to him again and he will ask for some Belladonna flowers. You should have found some in Dradeel's house but you can also pick some from two patches just north of the village. He will tell you these flowers are for you, this prompts some romantic dialogue before he leaves.
If you hold these flowers, you won't be affected by lycanthropy curse, thus won't die after several days if you don't kill Mendas, only works on main character.