This is as likely a magical object as a gaming die. Glass would have been expensive for a mere gambling device, whereas bone dice were cheap. It's a Platonic solid found in Egypt, the epicenter of Neoplatonism. And the symbols on the sides are astrological.
In Middle Ages and before, games and magic and religion weren't separated. Even mundane games played in taverns were magically bound to your luck and well-being. More sophisticated (board) games were outright sacred and were seen as a way to communicate with gods.
Wiki has several examples from the Bible, casting lots to see what God chooses.