nymph amulet 
Aquire the potion of youth from the magician in the mining town
you do this by asking the magician about "youth potion" 

Then go to the witches hut in the north forest.
There are three skeletons in the dark before you can enter the hut.
Then go in and give the potion to the witch, she then disappears, leaving the nymph amulet upon the ground.