Final answer:
Zarathustra, the founder of Zoroastrianism, had a mystical religious experience where he encountered the supernatural and had a union with the deity or supernatural.
Step-by-step explanation:
Zarathustra, the founder of Zoroastrianism, had an astonishing religious experience described as an encounter with the supernatural. He had a mystical experience and union with the deity or supernatural. This experience led him to receive divine messages and teachings, which became the basis of Zoroastrianism. It is important to note that the exact details of the experience are not provided in the information given.