To use this item you simply write a question on the parchment. Any question of any complexity will do. When the question is written in full, the ink will absorb into the parchment. It is is then placed back in its case and left overnight. Be careful what you ask, for there are many things that should remain unknown.
In the morning an answer to the question will be written on the scroll.
The magic used to create and use this item is a type of necromancy, and like all necromancy it can be unpredictable and dangerous. The scroll summons a spirit that can see and access most mortal, astral and ethereal knowledge and then relay that information to the scroll. But there is always a price to be paid for such information, in this life or the next.
If you're lucky the summoned spirit will just leave you alone and go back to whatever dimension it slums around in. But sometimes the spirit will linger and decide to haunt you a bit, or in the worst case scenario it might decide it likes you and wants to be your friend and companion... forever.
You see, spirits are lonely and miserable sons of bitches, and having one as a friend is a surefire way to make a person equally lonely and miserable. You generally don't become a spirit without some sort of onerous debt in your past that left you forever locked in between worlds, incapable of moving on, but equally incapable of letting go.
|Hug me, I'm so desperately lonely.|
As you can see the ghost scroll has both advantages and disadvantages to its use. The stats for a chance of "spirit friendship" or "haunting" are up to the GM and can be tailored to their campaign. I might also say that the risk is directly proportionate to the complexity/revelatory nature of the question, that might encourage players to not ask things like "what's the meaning of life?" But then again as the GM you can be as devious as you want and just answer "42", and then inform the player that a really irritating spirit is now his characters bestest friend.