Unfolding the flimsy and spreading it across your knees was the final gobbet boiling off the skeleton. The letter was written in Ninth House crypt-script; your own cipher, based off that of your parents and developed when you were seven years old. It was unbreakable to anyone who lacked your rosary, Marshal Crux, and a hundred or so years to spare.

Harrow the Ninth - Act One, Chapter Four