The Celestial Tower

Celestial Calamity War, the greatest war fought between good and evil in the entire universe has lasted for a trillion years. During the war, many heroes emerged, many fall, from both sides namely the celestial race and the demon rase, but no matter how much they tried no side was able to emerge victorious. The universe was in chaos. At least a one in a trillion year genius emerged in both sides at the same time, The Celestial Emperor and The Demon Emperor. They fought for ten thousand years and end the great war. The Celestial Emperor emerged victorious though with severe wounds caused by the last all-out attack by the Demon Emperor. Because of the corrosive effects of the attack, no medicine can cure the wounds and he is in his death bed. He knows that he won't last long. So, he created a Devine artifact. The Celestial Tower, with 11 floors, each floor is a separate world it self. He created a AI system to run the tower. The motive is to find a worthy successor to inherit his legacy that he placed in the top, 11th floor. He scattered all his possessions in the tower. He made various dungeons, Mystic realms, secret inheritance of his fallen comrades, various life threatening dangers and breeded numerous demonic beasts and choose billions of geniuses of different race from all over the universe and send them to the very 1st floor to compete for his legacy. And then passed away. But as soon as he died then the demon race's last survivors in order to regain their power and to prevent the emergence  of a new celestial emperor invaded the tower. The tower system furious, retailed by posting missions after missions preventing the demons to gain too much power. They has already invaded all the 1st ten floors and made a stable footing after persevering a hundred thousand year. After all those years, the original summons have all died. They married each other, multiplied inside the tower and the letter generation have long forgotten what they were doing in the tower.  How they come here or even if there is any thing outside the tower (same for the demons). The both side only knows that they have been fighting each other for a long time and they will continue this fight. In all those chaos, the original goal of the tower's creation was long forgotten and from situation who knows how many eons it will take for the system to serve its original purpose. Frustrated, it has finally decided to summon a second batch of players.