I believe a world after celestia should be ice, myth and death. It is for lvl 60+ ( + if they raise level cap ) and is an underground city. Some history about what I am thinking
A tale is told of a city for everyone, but it is in the middle of a frozen wasteland. Many people flock to see the grand opening, but they must wait a long time. After 5 weeks a bell rings and the gates open. A sign outside reads: Pick your house. If you get to the castle, then you are the royalty of the city. If all the houses are taken because you werent fast enough, you live on the streets. People tried to get to the castle but many died through fights over it. Finally, The Ikradomadesh family won and named the city Ikra. Many months later the people decided to lock the guards outside the city. They said that there was a fight going on in a lumber mill to the south, so the guards went to check it out. When they got back the gates were locked and the banners of the king of that area being torn down. The guards made a camp to the east and called it village of the ancestors ( commons area for this world ) With the guards out of the way there was no law, so the people became more evil, bit by bit.
Many years later a spirit arrives at the city gates. It said ' Let your protectors in or your city shall fall to the depths of the underworld! ' The people refused, so she began to walk away. As she walked her first steps, she felt the ground tremble. She looked back and saw the city sinking under the ground. She started smiling a evil looking smile, even though she was a good princess, and said' They got what they deserved '. When the ground stopped shaking only the tip of the castle reached out, but it started raining, and now the city was in a crater, so the rain washed all the dirt on top of the spire. The city became a legend, and the spirit dissapeared
Village of ancestors- Commons area Frozen wastes- Ice area Lumber Mill- Myth and Ice area Flooded barracks- Ice area Market square- death and some balance area Graveyard- Death area The Mine- Dungeon Palace gardens- Myth area Palace sewers- Myth area Supreme court- Mixed area Hall of the wicked- Finishing Dungeon. And some side dungeons to make up for the low amounts of dungeons. Forbiden forests- Found off Lumber Mill Palace escape route- 2 entrances One from supreme court another from Market square