Veil

"Then I saw a new heaven and a new earth, for the first heaven and the first earth had passed away, and the sea was no more. And I saw the holy city, new Jerusalem, coming down out of heaven from God."
The barrier between the physical world and the spiritual world is The Veil. Eventually, some Adepts acquire the power to cross the Veil and travel the roads of angels and demons.  But with the exception of Orders like the Celestials, Infernals, Theists and Saviors, most Adepts won't gain this ability until they are Veteran status, if ever.
The Veil is a hard place to describe: the "area" near the material world is most like the material world itself, there is space, time and motion. But the 'farther' out you go, the more it transforms into... other things. Those Adepts who are old and powerful enough to venture that far out return with strange tales indeed.
Category:God
Category:Spirit
Category:Celestial
Category:Infernal
Category:Infinity
Category:Inquisition
Category:Eldritch