In reality , it was sand . Sand used to make the finest glass . After the war , the Barcid king had ordered that no glass was to be given to outsiders at any cost . Thus , over the years , glass had become scarce and the process of glass making lost to the world .
Question: What is the reason the Barcid King ordered no glass was to be given to outsiders ?
The answer to the above question:


He wanted the glass making trade to be rarer and his kingdom would be known for it .