Mysterious Stone Hunting Challenge

Jon was confused, floating in a void. A voice spoke to him. "Before you ask I have no name and I am nothing just a very ephemeral entity born of your wish," It said ", The stone shall be hidden in a magic box which only you can open, unless you die of course. It will then be hidden somewhere within it's range. I believe that qualifies as interesting. Oh yeah and until you find it, stuff will happen, I won't tell you what but it will happen within the stone's new range, use that info to your advantage. Well I'm going to cease to exist now, bye."
"Wait," said Jon ", What does ephemeral mean?"