The Book of Rust

The book contains the myths, and lore of a nameless god known only as the "Good of Rust" or, "The God of Decay". The five-armed, one eyed entity is one of the Great Old Ones, a entity who revels in, and draws sustenance from corruption and decay. Though owing to the gradualness of his work, he might more accurately be called a god of entropy.

The god is accompanied by invisible servator spirits called Eun, who carry out the gods work on Earth, and can be summoned with the right formula and sacrifices. It is assumed that the books author, the Frenchman Évariste Barreau, died as a result of an improper summoning, as one of the Eun's many powers is to cause rapid purification.

The book itself is a long-winded tirade, filled with many formula, and essays on the god itself, and stories collected from unknown locations around the globe. Though worship of the God seems to have originated in western Russia, today there appears to be no sign of this once obscure cult. Presumably its worshipers were disbanded or wiped out during the era of Soviet oppression. So that today, all that is known of the god, or its cult, is in this book. and even then, who's to say it isn't simply the raving imaginings of a long dead wizard?

Still, the book does appear to contain actual mystical properties. Tests have revealed that summoning incantations are genuine, and the simple iron trim will occasionally seep a rusty fluid, yet strangely, never seems to deteriorate. As a precaution, the book is kept in a dry, specially sealed vault in the Miskatonic archives.

After extensive testing,  access to this, like all other tomes of elder lore, was added to the restricted list, accessible only through special written permission of the school archivist.