Principia Harmonia is the primary holy book of the Mythics of Harmonia. It's uncertain whether this is a completed book or a book in progress.
The book focuses on the worship of Harmonia, whom the Mythics see as the misunderstood Aneris, sister of Eris or Discordia. While traditional Discordians claim Aneris is the Goddess of nonexistent things, and is responsible for death, in Babysitter Eris the Mythics claim that:
....the real Aneris doesn’t make anyone disappear who doesn’t want to, and helps innocent people escape persecution.