Edmund M1(2), you will learn about the chest which you can find right next to one of the cottages. The key can be found on the training square right next to the goblins camp. Head to Sonja to unlock the passage and begin the training M1(7). In the chest you will find a vial that will increase your intelligence and a scroll that will increase your defence.
Afterwards take the skill book from the top of the mountain. Thanks to it you will increase your lockpicking skill. Open the chest by the magic teacher, Alberic M1(5). Inside you will find a weapon.