To get this, you need to recover HP using any of the healing items in the game: chickens, the Pummarola item, or evolved weapons e.g. Soul Eater or Bloody Tear. This is cumulative, so you'll get after a few runs through the game. It will pop at the end of the run when you reach a total of 1000 HP recovery, and you'll unlock the character Suor Clerici for purchase.