What information do we have on the real vision of Pope Leo XIII? There are a lot of stories, like this one about the vision of Pope Leo XIII which prompted him to write the prayer to Archangel Michael. Stories of a conversation between Jesus and Satan, often being tied to Second Vatican Council etc.  

However, what true historical information do we have on the vision? Are there any official documents as to the content of the vision?
It appears we have no true historical information on the alleged vision of Pope Leo XIII.  The Global Catholic Network says that in 1934 a German writer, Father Bers, investigated the origins of the story of Leo’s vision. “Wherever one looks,” he observed, “one may find this claim — but nowhere a trace of proof.” Father Bers quoted a priest who visited with Leo XIII when the prayer was instituted in 1886: 


  When the prayers which the priest says after Mass were being instituted, I happened to have a short audience with the Holy Father. During the conversation Leo XIII mentioned what he was going to prescribe and recited all the prayers from memory. This he did with such deep-seated conviction of the power of the cosmic rulers of this darkness and of the beguilement which they cause, that I was quite struck by it.  


Father Bers concluded:


  Therefore it can be safely assumed that the Holy Father would have spoken of the vision if he had had it — or that at least the reporter would have mentioned it — since it would have been most relevant to the general purport of the statement. Consequently, the argument “from silence” seems to indicate clearly that the “vision” had been invented in later times for some reason, and was now feeding upon itself “like a perpetual sickness.”


The article goes on to summarise the problems with associating the supposed vision with the institution of the St. Michael prayer:


Writings which promote the story give no references to sources.
The various accounts contradict each other as to where the vision
supposedly took place — after Mass at the foot of the altar, or in a
conference with cardinals.
The various accounts are inconsistent about the date of the vision.
The dates the accounts give for the alleged vision (1880, 1884 and
1888) do not correspond with the date when the St. Michael prayer was
actually instituted (1886).
There appears to be no corroboration for the story in a contemporary
account which one would expect to have mentioned the event, had it
indeed taken place.