After you escape from the Gortress and return to the Observatory, Apus Major goes with you to the Realm of the Almighty.
Explore the Realm
Go up the glowing stairs to the north and check on the doors at the top. When the doors unlock, go through and continue going up the stairs. At the top, go to the left and down the stairs there, and enter the building to find a chest. It contains a White Knight's Shield. Then go east and continue going north up the stairs.
You will reach another area. Go around the circular rainbows to get a Mighty Armlet from the red chest. Then continue going north to reach a palace. Go inside.
You find that something is amiss. Go to the stairs in the northwest corner or northeast corner of the room and go up. You will be in a room with grass on the floor. Walk up to the light in the northern part of the room. The others will come upstairs. Apus Major gives you the Fyggs. Walk up to the light and check on it, then offer the Fyggs. Watch the cut scene.
You find out that there is an evil being who was responsible for bringing back the Gittish Empire. This evil one wants to destroy the world. You have to go to the heart of the Gittish Empire and destroy this source of evil.
Afterward, you will be back at the Observatory. Talk to Stella and Sterling. When you are ready, enter the Starflight Express. Talk to Sterling twice and he will give you a list of destinations that you can go to. If you are ready, choose Gittingham Palace. You will land in front of the blue tree in the Gittish Empire. Walk north and you will reach an evil barrier. After you bump into the barrier, Celestria will remove it for you. Go north to enter Gittingham Palace.