The power of prophecies, sorcery and witchcraft go hand in hand throughout the history of mankind, and there is irrefutable evidence of its power and its truth. An Oracle is a form of communication with higher spirits (call them Gods or Angels, as you believe), so that such celestial beings help unveil revelations to whom it seeks such spiritual help.
When an oracle occurs the conjured spirit then uses the body of a spiritual priest or priestess (a witch, a clairvoyant, a sorcerer, and so on) as a means of communicating with humans, and vice versa. Out of the oracles were born some of the most important prophecies that we know.
The oracles of Zeus were the most reputable and famous in the Greek-Roman era. The oracles of Zeus were performed in various shrines, and they were sent by the spirit of the God to his priestess so that they would reveal it to those who visited the temple;
The priests received the oracle by contact with the spirit of a God through "incubation": at night, always walking barefoot, they slept on the floor of the temple. The spirit of the God that lived in the sanctuary would then contact the priest or priestess through dreams or «night visions»; the very same happened with the biblical prophets as the Lord God spoke to his prophets by dreams, Daniel is the most famous biblical example of such a way of communication with the divine.
Alexander the Great consulted the oracle of Amon (homonym of the Egyptian god Zeus in Greek culture) to learn about his divine filiation, as well as about the fate of his enterprises. It was revealed to him that it was the son of a god, and that he would be the greatest conqueror of all time. This proved to be true, and even during Caesar and the great Roman Empire, the deeds of Alexander the Great echoed as legends made impossible match.
The oracle of Delphos was another of the most famous means of spiritual contact with the gods. The god Apollo spoke with those who sought assistance through his priestesses. It is certain that once, the king Creso consulted the Oracle of Delphos in order to determine whether to attack Persia. It was answered that if he attacked Persia, he would destroy a great kingdom.
The king thought that the response was positive and made war against Persia. In the end, it was his own kingdom that was destroyed, and the prophecy therefore did not lie. Indeed, the spirits speak through the mouth of a prophet, and in so doing it they dictate their sentences. One must accept their words with prudence, not wanting to turn the spiritual messages into what we want them to be, but rather in what they really are.
A Hebrew who lived between 70-100 AD, named Hanina ben Dosa, was a famous healer who lived in Galilee. In those days, the son of a remarkable man named Gamaliel was ill with a severe fever. Gamaliel sent two followers to Hanina, asking him to come and heal the child. However, instead of leaving with the employees of Gamaliel, Hanina rose to the top floor of his house and prayed.
Because of this gesture, people ask him with some suspicion and irony: "Are you a prophet?". Hanina said: “No, I am not a prophet. But I have this gift: if a prayer exits my mouth with fluency, I know that there will be healing; But if it doesn’t happen, I know that there is no cure.” The two men departed for their master’s house and soon discovered that at the time Hanina made his prayer, the boy had actually healed.
In Greece's s, many people resorted to the temple of Asclépio, a divine spirit that granted great miracles of healing to those who sought his aid. The historical facts say that some time a sterile woman stayed overnight in his temple, because she desired to be able to have a child.
During the night she slept in the sanctuary, the woman dreamed that one of the sacred serpents of Asclépio penetrated her. The woman went back home the following day and got pregnant, against all the odds, and that what was one of the many miracles that the spirit did to those who looked for his help.