In the Uninvited Guests quest, you have to block the second tunnel used by Kassynders soldiers to enter the mines.
This quest continues the events started in the previous mission, called Enemy at the Gates.
Quest: Travel to the Western Tunnels
You are inside the southern tunnels and you took care of the first breach.
Exit the room where you set the first explosion and save your game.
Continue down the tunnel and return to the platform you used to get here. Use the platform to get to the other side of the cave. Go left and take out the Azunite warriors you encounter, and then continue.
Follow the tunnels forward and you will eventually reach the Deep Well.
Go all the way up and make sure you dont follow the corridor on the right, which takes you to The Tumbledown Court. Continue straight ahead.
Look on your mini map and you will see the entrance to the Western Tunnels. On the right side is a small area where you will find additional Painite deposits for Phineas. Pick them up and then proceed through the door that takes you to the Western Tunnels.
Follow the tunnel and talk to Roderick, who will also ask you to find the Trapped Royalists. The quest is called Building Bridges.
You also have to find four satchels of explosive powder, in order to close the breach.
Quest: Gather Explosive Powder
Enter the Western Tunnels and save your game.
Move forward and kill the Azunite warriors, then enter the door.
The first satchel containing the black explosive powder is behind the door, near a corpse, to the right.
Pick it up and follow the railroad.
Follow the tunnel to the right, and then right again until you will see a Cyclops. Kill it and make sure that in the next tunnel you go to the right again, until you reach a ramp.
Follow the ramp up and use then red crystal on the left to lift the first incinerator platform.
The second incinerator platform is to the right and the third is to the left. Both of them are marked on your mini map, and both of them are protected by Azunite soldiers.
Activating these platforms is the only way to complete the Building Bridges quest. After you save the Royalists, make sure you investigate the room where they were trapped, because you will find three chests and the second satchel containing explosive powder.
Return to the main corridor, and assist the Royalist soldiers fighting the Azunite.
You will have to go up on a ramp, to the right, but before that, make sure you pick up the third satchel of explosive powder, located near the ramp, to the left.
In the next area you will see a mining cart. Near the cart is the fourth black explosive satchel. Pick it up and continue forward, until you see a red crystal in front of you.
Use the crystal to activate a platform which will take you to a secret area. Open the chests there and pick up the items you find there, and then return to the main path.
Follow the tunnel to the right and you will enter a large chamber. Kill the Azunite soldiers, and then go left, and you will see three large cannons, and a platform. Use the platform to get to the other side of the cavern.
Kill the enemies you encounter and then explore this area. Here you will find more Painite, and you will complete the All that Glitters quest. Use the next platform to advance, and when you reach the other side, save your game.
Kill all Azunite troops and set the explosive charges, turn back.
You have to escape the tunnels, but be very careful, because you will be attacked by cannons and more troops.
Use the GPS if you are lost and return to Queen Roslyn in the Tumbledown Court.
Make sure you turn-in all quests you completed, and get your rewards.
Queen Roslyn will give you a new quest, called Ebb and Flow.