Your world-building is fascinating! Here's a refined version of your description:
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**Demonic Realm**
The Demon Palace stood as a dark, imposing fortress at the heart of the demonic realm, its towering spires piercing the blood-red sky. Constructed from obsidian and brimstone, the palace exuded an aura of malevolent grandeur.
Massive iron gates, adorned with grotesque carvings of demonic faces, guarded the entrance. These gates creaked open to reveal a grand courtyard, where twisted, blackened trees with fiery red leaves cast flickering shadows on the ground.
Inside, the palace was a labyrinth of shadowy corridors and vast halls. The floors were made of polished onyx, reflecting the dim light of torches that burned with an unnatural, greenish flame. The walls were lined with tapestries depicting scenes of ancient battles and demonic conquests, their colors vibrant yet sinister.
The throne room, the heart of the palace, was a cavernous chamber with a vaulted ceiling that seemed to stretch into infinity. At its center stood the throne of the Demon Emperor, a massive seat carved from obsidian, adorned with spikes and encrusted with blood-red gems. Above the throne, an open space allowed a view of the sky, though it was protected by a barrier for safety.
In the private quarters of the Emperor, the decor was no less opulent but carried a more personal touch. Silken drapes in deep purples and blacks hung from the walls, and the furniture was crafted from dark woods and adorned with intricate carvings. A large, canopied bed with velvet curtains dominated the room, and a fireplace crackled with blue flames, casting an otherworldly light.
The palace was a place of both beauty and terror, a fitting residence for the ruler of the demonic realm.
There are four kingdoms in the demonic realm: the Kingdom of Bezoril for land demons, the Kingdom of Fireitren for fire demons, the Kingdom of Aquari for aquatic demons, and the Kingdom of Aeriel for winged demons.
Under these four kingdoms, there are many clans. Some demons have powers similar to those of other kingdoms but belong to a different kingdom. For example, gold red fox demons and red fox demons possess fire powers but live in the Kingdom of Bezoril. While there are various types of fox demons, the gold red fox demons are the highest-ranking clan.
Each kingdom has its own king and other royals. The king is the most powerful of all clans in a kingdom, and if any demon wishes to become king, they must duel to the death with the reigning king.
However, the selection of the Demon Emperor is different. They are chosen either by the skies or through a duel to the death. Demons believe that if a Demon Emperor is chosen by the skies, it signifies fate and that the realm is in good hands. Nevertheless, a demon can still challenge the Emperor to a duel for the throne.
**Heavenly Realm**
The heavenly realm consists of the Realm of the Gods and the Immortal Realm.
The heavenly realm is ruled by the Heavenly Emperor, while the Immortal Realm is governed by the Immortal Lord. However, this does not mean that the immortals do not answer to the Heavenly Emperor.
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This book may not follow myths and legends of different cultures. I am the writer; it's the world I created.
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I hope this helps! Let me know if there's anything else you'd like to add or modify.