1. Talk to Sigmund on the 2nd floor of Lumbridge Castle to find out that there is a hole in the wall of the castle's cellar. He will request that you talk to the villagers of Lumbridge to learn more of what happened to the cellar.
   
   
   
   
2. Go outside and speak with Hans, Cook, Bob, and Father Aereck. One of them will explain that a goblin-like creature with bulging eyes broke through the wall.
   
   
3. Head back upstairs and speak with Sigmund and the Duke of Lumbridge. They will request of you to investigate the hole in the Cellar.
   
   
4. Enter the Lumbridge Castle cellar through the kitchen, and go to the back of the room to see a large pile of rubble blocking a hole in the wall. Try to break through the rubble by using your pickaxe on it. Once you have managed to clear the rubble, ignite your light source and squeeze yourself through the hole. Walk a bit further and pick up the brooch of the ground.
   
   Note: Before you enter the labyrinth, head a bit south of where you found the brooch to find a blocked up passage. Use your pickaxe to clear the rubble, similar to the passage in the kitchen's basement. This passage will enable you to return to the start of the labyrinth much faster if you trigger trap inside of it. Simply head north from where you end up, and through the passage to find yourself at the start of the labyrinth.
   
   
   
   
5. Speak with Sigmund and the Duke once again. The Duke will suggest that you read about the brooch in the Varrock Library.
   
   
6. Head to the library in Varrock, and show Reldo the brooch. He will tell you to search the bookcases in the western part of the library. Search one of the bookcases to find a book on goblin tribe history. Read the book and compare the symbol on the brooch with the drawings you found in the book.
   
   
   
   
7. Make your way to the Goblin Village. Once there, talk to General Bentnoze or General Wartface about the Dorgeshuun Goblins. They will then teach you two goblin emotes (Goblin Salute and Goblin Bow).
   
   
   
   
8. Head back to the Duke and Sigmund and tell them about what you have discovered. Next, head into the cave once again through the kitchen and make your way through the labyrinth of tunnels. Watch out for traps, if you trigger one you will end up in the Lumbridge Swamp Dungeon. Follow the route on the map below to navigate to the end safely.
   
   
   
   
9. Near the exit of the mine, speak with Mistag. Before you talk to him, you must do the Goblin Bow emote you learned earlier. Mistag will then begin to talk to you and will explain to you why his tribe is hiding from the "Surface Dwellers".
   
   Note: Instead of going through the maze of tunnels you can talk to Mistag to take you back through the tunnels.
   
   
   
   
10. Report back to the Duke and Sigmund. Sigmund will say that the Duke's silverware was stolen from the Cellar. The Duke and Sigmund request of you to ask around to find this silverware. Pickpocket Sigmund to find a key. Go to the room next door and open the chest with the key to find HAM Robes.
    
    
11. Head to the HAM Hideout east of Lumbridge, opposite the cowfield. Pick the lock on the mine entrance and descend down the ladder. Now, search the first crate you come across to find the silverware.
    
    
    
    
12. Return to the Duke and Sigmund to discover that Sigmund was the one who stole the silverware. The Duke will fire Sigmund and give you a peace treaty to give to Mistag. Bring the treaty to Mistag to complete your quest. You will see a cut scene of a meeting with Duke and Ur-tag.
    
    Note: Instead of going through the maze of tunnels you can talk to Kazgar near the entrance to take you to the end.
    
    Congratulations! Quest Completed!
    
    
    
    

Additional Information:

Upon completion of the quest, you may sell iron and silver ore to Mistag. For more information please refer to the Mining skill guide.

Wandering around in these caves is Nardok He will sell you a variety of bone equipment.