The skull's name is unknown, and because of his diamond-like bones, people called him the Black Diamond. He hasn't minded so far.
In the Sky World, he was probably the oldest living being. His life history is unknown, only he himself knows.
He might not be the most powerful, but he knew many secrets, something even great magi were curious about.
Rumor has it that he had even gone to another dimension that was as large as the dimension where the Sky World was.
If it was just going to another dimension, that would be normal, but even Arthur who was already a Great Magus, the dimensions he visited were always small.
What's interesting is that he opened a service to ask him. However, you don't ask him directly, but you ask an artifact he made that has all of his own knowledge so that when it is asked a question, it has the ability to give an answer based on that knowledge.
On earth, it might be similar to AI.
Of course, in magical terms, it would be called an artifact spirit.
