The Book of Proliferation is said to have been dated before the fifteenth century. The Styx title means "from one comes many," referring to The Phase. According to Eddie, after The Phase of the fifteenth century was stopped, only a few of the books survived. Eddie smuggled one copy out of the Styx Citadel and brought it Topsoil with him to show Will and Drake the secrets of The Phase. This copy is currently in Eddie's possession.