"In order to be in the Occultum, the Occultum must be in you."
When humanity was exiled from the Garden of Eden, God hid it away by compressing this alternate realm into an orb and hiding it somewhere on Earth. This orb eventually became known as the Occultum: a sacred artifact of divine origin that even predates the lore.
For centuries, it was housed in an ancient temple until it was looted by invading Mongol hordes. The Occultum would eventually be traded on the black market. By 2009, the Occultum came into the possession of the Jacobson family, but when Hyram Jacobson's son fell ill, he traded it to the faith healer / angel Sister Jo in exchange for her healing his son. Jo later gave the Occultum to the demon Ruby with the plan for them to ride out the Apocalypse inside. Ruby was subsequently killed after hiding it and had refused to tell Jo where to find it, knowing too well that she can't be trusted.
In 2020, Castiel manages to contact Ruby in the Empty and recover the Occultum, which she had hidden in a church guarded by hellhounds. When Jack consumes it, the Occultum absorbs him and sends him to the Garden of Eden, where the serpent restores his soul before returning him to the church and killing the hellhounds. The Occultum is currently in the Men of Letters Bunker.
The Occultum, whose name is Latin for "hidden", has the appearance of an ornate orb, inscribed with an Enochian passage that reads, "In order to be in the Occultum, the Occultum must be in you." The Occultum itself is the Garden of Eden: an alternate realm compressed into an orb by Chuck following humanity's exile. When used by a non-human entity through ingestion, it transports them to the Garden of Eden.
- The concept of the Occultum resembles the theory of pocket universes, dimensions that contain individual universes with a finite amount of space.