The Formula

The Formula of Power
 The Formula of Power  is a Hardmode item that allows you to create a magical Hardmode item of choice. (All weapons above 75 damage are removed from selection list )

It can be purchased from the  Wizard  for 100 Platinum.

There is a way to obtain it pre-Hardmode, and it is to purchase it from the  Dryad  for 1000 Platinum or the  Traveling Merchant  for 500 Platinum.

The Formula of Power Statistics