Head to the Rookridge Inn and talk with Hammer. After a conversation, Hammer and Theresa will both tell you to take it easy for a while. Fortunately, thanks to being away for 7 years, there are some brand new side quests available.
It’s also a good time to catch up on some you have not previously completed, do some exploring and catch up with your family or families if you like. After a short while, Theresa will ask that you return to the Hero’s Guild.
Following the story sequence, we find out our new objective, returning to Brightwood Tower to use a Cullis Gate. When you are ready make your way through Bower Lake back to Brightwood. Follow the path down the hill to a locked gate where Garth and Hammer are waiting for you. Garth knows of an alternate entrance to the tower, so follow his lead you will eventually reach a statue on a hill overlooking the entrance.
After the conversation, once again follow Garth. You will have to fight quite a few Spire guards so if you have any trouble, just stay close to Hammer and Garth and they will assist you. When you reach the top of the stairs, and you pass through the giant archway, a Spire shard will attack you. Defeat this and head round the corner. Defeat another two groups of Spire guards for safe entry to the tower. Once inside, head up to the roof to start a scene.
Garth will activate the Cullis Gate, and will be unable to defend himself. At this time, another shard appears and summons a large number of enemies to try and disrupt Garth. You must protect Garth as he opens the portal. The enemies will originate from the stairs that you came from and the tower opposite.
Initially the enemies will consist solely of melee Spire guards, but as Garth gets closer to completing the portal, you will be attacked more and more frequently by both melee and will using Spire guards. When the portal is completed, polish off the remaining enemies and use the gate.