Haunted Houses & Uninvited Guests.

This is a real story who sees two of my good friends "victims" of what follows:
One of them that I will call "F", had a family villa a long time ago, it was huge, with a "creepy" cellar that gave me the chills everytime I entered it (I was used to spend holydays and some week-ends in my childood there), but the cellar is not the place I am going to talk about.
It was a house that belonged to a Count who actually owned a Castel in Tuscany (I will talk about it in the future), so in the basement there were displayed knights' armours and weapons like swords, daggers, speares and shields, all of it seemed to belong to the medieval period.
So my friends, ("F" and "C"), when they were about 20 or 21 were used to spend the summer week-ends alone in this I would say mansion.
Let me give you a fast description of the house that was on a considerable big property: there was a guest house, a cellar and a basement on the lowest level, the ground floor had 2 living rooms (one with a characteristic fireplace), and the second floor had 6 beedrooms that faced on a living room in the center of the floor.
They used to sleep in the first bedroom on the left coming up the stairs and one night  they had an idea: switching off all of the lights in the house and going upstairs and in their bedroom in the dark...
So, the lights are off and one next to the other started to walk in the dark. Once they were on the second floor their eyes were already used to see in the dark and they reached for the bedroom...
They opened the door when they see suspended in the air in the middle of the room, this little "man" who appeared to be sitting (but it was in the air) and was looking with a serious expression on his face at a ball that he was holding in his hands from which a very strong blue light was coming out, to the point that all of the room and this "man" were blue, illuminated by that object.
They ran as fast as they could and apparently the dark house and the stairs on their way out, did not pose any problem! They were so scared that they did not re-entered the house... They stayed outside all night long until the next morning and waited for F's father to arrive and check the house... But naturally, he did not find anything strange.
F and C were so scared that years after it happened, they still did not want to talk about it.