When you arrive in Nordinbad you will see that the fortress was indeed attacked.
Nordri and Bruni fight for their lives, and you must help them. Unfortunately Bruni is defeated and he falls in battle, but all is not lost.
Get ready to kill Agandaurs forces and protect the dwarves.
Main Quest: Repel the invading forces
As soon as you arrive clear the fighting area. There are two turrets to your left. Make sure you use them to dispatch the archers downstairs.
When all forces are killed, your objective will change.
Main Quest: Destroy the siege towers
Using the same turrets, destroy the siege towers that appear near the walls of the fortress.
Try to kill the troops that spawn, otherwise they will get near you and you will be overwhelmed.
Keep in mind that you have to move from one turret to another, and only if you destroy all siege towers you will be able to advance, and receive a new objective.
Main Quest: Protect the Inner Door from Goblin-sappers
This objective is a tricky one and you must move very fast if you wish to complete it.
A good idea is to position your hero in front of the inner door and fire your arrows as fast as you can.
Remember that the sappers will attack in waves coming from both sides. If the door falls you will have to restart.
If you successfully complete this objective, your main quest will change again.
First watch the cutscene showing Beleram who comes to help you, then get ready, because some trolls will appear and you must kill them all.
Maintain your position and try to distract to trolls. If they reach the gate, the damage they inflict is greater. Make sure you keep them occupied.
After the trolls, you must slay a Siege Commander.
His melee attacks are very powerful. Avoid them by dodging and dont let him catch you unprepared.
Kill him and you will complete the main quest.
Watch the cutscene and you will unlock the Siege-breaker Achievement/Trophy.
Now, go inside Nordinbad, but dont forget to loot the chests near the main entrance.
Gorin will wait for you and you must talk to him. You will complete the quest called Aftermath and you will receive a new quest called Beleram.
To complete this quest, you must talk to Beleram. He is inside the fortress, in a small room to the right, while facing the main entrance.
Repair your items, talk to Beleram, and you will receive a new quest. A new destination will be unlocked on your map: Carn Dum. Exit through the front gate to start the eighth chapter of the game.