I'm a quick thinker, be careful what you wish for.
If I make it, Void Blasphemy will be the ability to commit any sin you desire, no consequences. Not from earthly law, or divine law. Also, it enhances any sin or evil-based powers you have.
This comes at the cost that you must never subscribe to any religious system (even cults), and you must renounce any that you currently subscribe to. Oh, AND, if there turns out to be a Heaven (which I believe there IS), then you don't get to go. Though you don't go to Hell either. You spend eternity floating out in the void, incapable of moving out of the dark, empty, fathomless limbo (unless, of course, God dictates otherwise).
“…Judge not what a man has done, but judge what he could have done if he was a different bloke altogether. For art thou a leper? And a leper can changeth his spots…” --Rudy Wade, Misfits (Series 4, Episode 8)