The Order was founded by the Pact and Bequest, or Knightly Bestowment, of which almost nothing is said in the story outside of its existence and the fact that there are holes in it which allow weird things. The Bequest gives the Knights a number of mystical powers, including healing, access to information from the Library and a secret language. Healing requires payment. Typically, this is three seconds of Hell, followed by Purgatory and Heaven. Satan seems to want to play with Petra Donner a bit, and send her back with messages written on the inside of a live python's skin.