Mankind has many weaknesses but one stands out beyond the rest. One out of many.
The Weakness of Man is knowledge bestowed upon another by a knowledge bringer. The Weakness is to be used as a weapon against man, if man ever grows powerful enough to destroy time, and space itself. The weakness is passed down from knowledge bringer to another. To become a knowledge bringer, you must receive the knowledge of the weakness.
The knowledge of the weakness is to be given, only if a deal is struck between the recipient, and the knowledge bringer. When the deal is made, the knowledge bringer will take anything s/he desires, from the recipient, in return for the information. The knowledge is then passed on from the knowledge bringer, to the recipient, making him/her the new knowledge bringer. If the knowledge bringer is to die with the information, they are to be damned to hell. Thus the deal is made, to save one's self from damnation.