Once you have the Quarantomb Key, you can go with Dr. Phlegming to investigate the curse afflicting Coffinwell.
Enter the Quarantoom
In the Quarantomb, you can find a Slipweed, Mini Medal, and Seed of Skill.
To proceed, just go to the northwest and northeast corners of the tomb, and press the switch on the statue in each corner. Once you do that, the chamber in the center will unlock.
Go to the center chamber and check on the jar. The Ragin' Contagion will attack.
The Ragin' Contagion can attack twice in a turn. Sometimes he will attack two different people, and sometimes he will attack one person twice. He also knows Kasap and Deceratle. These decrease defense and agility.
Once the Ragin' Contagion is gone, you will get some Royal Soil, and Dr. Phlegming will be able to seal the contagion away again. Dr. Phlegming will go to the chamber below, where the amnesiac ghost of a king will be wandering, and Dr. Phlegming will be reading the tablet in the center of the room.
Back in Coffinwell
Return to Coffinwell and talk to the Mayor. Then go and talk to Catarrhina. Next, talk to the Mayor again and you will get a Feather Headband.
Now go to the church and talk to the ghost on the left. Then go check on Phlegming's door. After some dialog, the doctor will join you. Go around and talk to everybody. After a while, Phlegming will say that he has seen enough. Go back to his place and watch some automatic scenes.
Back to the Starflight Express
Your next stop is the Starflight Express. It's in the Mountain Pass, west of Stornway and east of Angel Falls. When you go inside, check on the controls and you will return to the Observatory.
You can go around and talk to everybody if you wish. Then go up to the top of the Observatory and pray to Yggdrasil. You will see some automatic scenes. Then you will learn Zoom, which lets you warp to any town that you have been to before.
Exit the area and you will see some more automatic scenes. Now go to the Starflight Express and talk to Stella. You will head down to the Protectorate and end up on Newid Isle. You can go to Alltrades Abbey to the northeast. That is your next destination.