After an animated scene showing the battle between Greygnarl and Barbarus, you will find yourself imprisoned in the Gortress.
Gortress Cell
Check on the door of your cell. Your next-door neighbor will talk to you. When you are woken up the next day, exit the cell, then go through the door in the small tower in the center. Go upstairs.
Gortress Outside
Talk to the guy at the end of the bridge. His name is Sterling. He will join you.
Talk to the guards in the south corner for short scene.
Now you can wander around. There is a priest to the left of the bridge who will save your game. The thief-looking guy near the priest runs an item shop. Check on the gallows just north of the jail cell pit for a brief scene with Sterling.
The eastern corner of the upper area has some people working as slaves. Check on the guard to see another scene.
The western corner of the upper area has a graveyard. Go up to it to see another scene.
In the northern area, up the stairs, check on the glowing wall for another scene. Sterling will ask you to touch the wall, so walk through it. It seems that the Gittish seal that you're carrying makes you immune to shield field's effects.
Once you have done all of the above, Sterling will tell you to go wander around on your own before work starts. You don't have to unless you want to save the game with the priest or buy some things from the item shop guy. Otherwise, go talk to Sterling near the bridge and say that you're ready to work.
The Escape Plan
Afterward, back in the cells, Sterling will tell you about the escape plan. Agree to help out.
The next day, go outside and go up the stairs to the main area. There's something going on at the gallows. Check on the guard and the guy being pushed to the gallows. Sterling will get all angry and knock the guard down, then he'll tell everyone how you can get through the shield fields to turn off the shield field generator.
Sterling will tell you to leave the Gortress and add more people to your party, then get all equipped and return. So leave the Gortress using the south exit. The Gortress has already been added to your Zoom list, so you can instantly come back here.
Get Your Other Party Members
After leaving the Gortress by the south exit, Zoom to Stornway and talk to Patty in the Quester's Rest and choose Call Up a Friend to get your party members to rejoin you. Then Zoom back to the Gortress.
Turn off the Shield Field Generator
Go to the guard tower in the northern corner of the Gortress. Don't go into the door at the base of the tower. Go up the stairs and into the door there. Inside, there is another set of stairs to go up, so go up.
There is a soldier guarding the shield field generator. Check on the guard to start a fight. It's a Lethal Armor. Once the battle is over, check on the shield field generator to turn it off. You can't do anything upstairs except look around, so go downstairs and back outside.
Follow Sterling
Sterling will meet you outside, then he'll go into the lower door of the tower to rescue the maximum security prisoners. Go into that door and step into the blue circle of light in the corner to get healed up. You can go outside and talk to the priest to save the game.
Back in the tower, go downstairs and examine the bookshelves on the left to learn some new recipes.
Now go back to the center of this floor and go into the throne room. Check on the giant pig guy to start the battle.
Lieutenant Goreham-Hogg
Goreham-Hogg will use physical attacks and might use Psyche Up to raise his tension. When you defeat him, he drops a Tough Guy Tattoo.
Sterling will take his whistle from one of the red chests. Open up the other red chest to receive the Ultimate Key. This key will open every lock everywhere. Before going downstairs, you can go back to where you and Sterling used to be locked up, and unlock every cell. One of the cells contains a Mini Medal that you can find by checking on a skull.
Rescue the Maximum Security Prisoners
Go to the left from Goreham-Hogg's throne room and go downstairs. Walk up to Sterling to start a scene. Apparently, these solitary confinement prisoners are Celestrians! Check on the cell door to unlock it, then go in and check on the cocoon. The Celestrian will be released from the cocoon. Do this with all of the cells.
The Celestrians say that there are more of them trapped in Gittingham Palace. The Gittish Empire has been feeding Barbarus with their power.
Go talk to Sterling after you have released all four Celestrians. There will be a scene and you'll end up in the Observatory at long last.
Talk to Apus Major
Go around and talk to people if you want. Then go to the second-to-lowest floor and talk to Apus Major. He will tell you that Aquila himself brought all of the fyggs back, so nobody believes your story of Aquila's betrayal.
After Apus Major departs, you can go around and look for any treasure that you might have missed. Then go up to the top level of the Observatory and talk to Apus Major once more. He will ask you about Aquila. Answer his question, then after he finishes talking, check on the door of the Starflight Express to go in.
Talk to Sterling to start the voyage back to the Observatory.