Well, without having read a particular 'Crown of Ptolemy fanfic', it's hard to say exactly. But it could be about the origin of the crown. Maybe it tells a story of how the crown was created in ancient times, who made it and for what purpose. It could also focus on the characters that interact with the crown in the fanfic's universe. Are they heroes trying to protect it? Or villains aiming to use it for their own evil deeds?
Ptolemy was an important figure in ancient history. He was a Greek astronomer, mathematician, and geographer. He is best known for his geocentric model of the universe, which placed the Earth at the center. His work in astronomy was highly influential for many centuries. He made detailed observations of the stars and planets and tried to explain their movements in the sky within his geocentric framework.
FGO isn't a typical visual novel. It has more gameplay mechanics and character-building features. The story is presented along with battles and strategic decisions.
It's not based on real events. 'The Last Days of Ptolemy Grey' is a piece of fiction that explores various themes and scenarios crafted by the writer's creativity.
There were the following FGO-related novels:
"FGO's Journey to the Other World,""Lu Mingfei Challenging FGO,""Starting from the Collapse of the World with the Card Drawing System,""Running FGO in the Ninja World,""King Arthur's Comic Journey,""Yuki's Holy Grail Journey,""The Story of Chaldeans Landing and Becoming the Director,""Saving the World from the Collapse," and "Chaldeans in Marvel." These are the different types of novels about FGO. There might be games-game systems, light novels-derivative doujinshi, funny jokes, infinite universe-infinite, and so on. I hope you like this fairy's recommendation. Muah ~😗