From the information I gathered from the H/P Wiki, it says that the veil is a barrier between the land of the living and the land of the dead.
Just wondering on this but what was the prime directive for keeping the veil? How did the Ministry of Magic come across it, and more importantly what information were the Department of Mysteries hoping to acquire since the Department of Mysteries is like the FBI and work on very top secret, undercover missions of some sorts and work of confidential nature.
Is this question answerable through in canon references? That would be highly appreciated. :)