Some tibian vocations have special places, where only that vocation can enter. Druids are not an exception. If you are a druid, try to find your own place an you will receive your prize.
Fernfang spawns here.
Go to Plains of Havoc and enter the Magic Forcefield located here, near some Orcs. You may find Giant Spiders on the way. You will be teleported to the Isle of the Mists, there you will find a Box and a Drawer on the ground floor, containing 2 Small Emeralds and a Book. Some times, Fernfang may spawn in the upper floor.