In those four you can either find the answer to their threat and win from the value and control of the Jace or just find the things your deck does and win with those things
This way, you get the potential benefit of opening a premium card in any color but don't have to worry about wavering between colors
To round out the deck, players added many of the generic Best cards in Standard. Coincidentally, many of these cards were available in Mono-Black
If you want to find the most expensive variant of Overlord of the Boilerworks possible, you can find the Fracture Foil starting at around $60
It is printed on the card it affects, or is granted to the token it affects by the effect that has created that token, or has been acquired by the object it affects through a copying or text-changing effect
Its only good for one unblockable hit on its own, so you need to surround it with other Clues to get a real advantage here