I remember reading a book a couple of years ago, and cannot, for the life of me remember what the book is called. I believe this spans multiple books.
The book followed the main character, I believe his name was Mar, through his life. The book starts out describing him as a thief in the city, he eventually tries to steal from some man, but the man catches him. Instead of reporting him, the man who caught him realizes that he has some innate talent, so he asks him to help him during his job. His job was to search the remains of an old civilization looking for magical artifacts, the first of which he finds is a scroll inside a metal tube.
After this I can’t remember what happened but he somehow gets stranded on a weird island with a decrepit castle. On this island he finds he can do magic and starts to make a raft out of spheres that he forms from sand. He then finds he can fly on this raft and floats over to a city which he finds under attack by the main antagonists, some religious group that likes to hoard magical artifacts from the old world. He saves this group with his newly acquired magic and they pronounce him king.