Stage 16 (Inside Information): The vault | Walkthrough LEGO The Hobbit Guide

Avoid the well-lit areas, which are at that moment investigated by Smaug

Destroy the objects in the area and do not worry about Smaug, for now. Your laud actions will not attract the dragon's attention prematurely. After you have smashed the right side of the area, hold down the building key/button to build a ladder. You will have to watch your steps only after you reach the location that is being watched by Smaug. You need to avoid the illuminated areas, which are being watched by the dragon or else, you will lose the entire health bar immediately. Wait for Smaug to turn to another area and go right then.

Pick up the flail and use it on the golden statue

You will watch a short cutscene, soon and your characters will enter the lower level of the vault, after a short ride down. Switch to Balin here and use his Dwarf Axe to cut through the cracked plate on the right. A flail will fall to the ground and you need to pick it up. Select this item from the inventory and use it to reach the big golden statue. After you do that, press the indicated key/button several times. Go right and wait for Bilbo and Balin to reach the lower level.

You need to build a new catch here

Also in this part of the vault, you need to go to the right, where you will reach another cracked plate. Smash it with the axe and then hold down the building key/button to build the right ramp. Of course, use the ramp immediately. After you get to the next area, smash the objects here and hold down the appropriate key/button to build a catch. You now need to use the flail that you have obtained, to reach the catch and rip it off.

After you destroy the weapon stand, you will be able to collect the bow

After you reach the lower level in the vault, select the axe again and cut through the cracked plate. At the same time, destroy the weapon stand, on the left, and pick up the bow (Lake-town Bow), as any of the characters. Use the bow now to hit the nearby target.

Move only if Smaug is currently, now watching the area directly in front of the characters

Wait for Smaug to stop belching fire and move to the right a bit. Just lie in the earlier phase of the stage, you need to avoid remaining in the areas investigated by Smaug (the well-lit areas). Wait for the right moment and dash to the right and hide behind the wall. Again, wait for several moments and when it is safe, clear your way to the artifact shown in the recent cutscene - Arkenstone.