Agrace, The Not-World, God’s Garden, the Vestibulum, The Third Kingdom

The shortest route between any two points is through Agrace. Some say it was once the Garden of Eden, abandoned by God since the Fall. Some say it is the Raven King’s third domain (after England and Faerie), leased from Lucifer until the Apocalypse.  Still others think it is simply a cosmic midden, where the refuse of Creation molders once it has served its purpose. Regardless, it is a perfectly interstitial space; it shares topologies with all worlds. All nations share a border with it; all rivers eventually drain into its ocean; all roads lead to its causeways. Enterprising magicians have found a way to use this to their advantage.
There are no teleportation spells in Pernicious Albion. Instead, magicians in a hurry must pry open a door into Agrace. This, naturally is extremely dangerous.
Agrace is silent and almost completely empty; its plains are a dark red, its seas a bitter green; its forests twisted and tired and grey. The sky in Agrace is always a pale gold.  There are neither rain nor clouds in The Third Kingdom.
Weirding Gate
Magic-User 3
Duration: 5 minutes, or until dismissed by the caster.
Creates a doorway between Albion and Agrace. Anything can pass through the gate as long as it fits, and remains in Agrace until it can find an exit. Distance works differently in The Third Kingdom, and so every mile travelled in Agrace translates to two miles travelled in Albion. 
By Zazisław Beksińki; a gnostic titan

 Denizens of Agrace are as dangerous as they are uncommon. There is a 1 in 10 chance of having an encounter per day. I will stat these up over the next few days.
  1. Corpus Inverter
  2. Debased Sorcerer
  3. Gnostic Titan
  4. Microcosmic Sun
  5. Travelling Fairy Lord-roll 1d4 (1-Duke of Sighs; 2-Bone Knight; 3-The Lady Electric; 4-The Lazarus King)
  6. Chaos of ravens
  7. Eternal haruspex
  8. Infernal dignitary-roll 1d4 (1—Alrinach, Whose Domain is Shipwrecks; 2—Agares; 3—Adramelech, the Hypocrite; 4—Ahriman)
  9. Heavenly ambassador-roll 1d4(1–Zephekiel, who rules Mercy; 2–Jophiel, guarding a tree; 3–Remiel, searching for a relic; 3–an angry cherub; 4–one angel and one demon, fighting)
  10. One of the winds-roll 1d4 (1—Boreas the North Wind, 2—Notus the South Wind, 3—Eurus the East Wind, 4—Zephyrus the West Wind
  11. Travelling Vampire Lord
  12. The Wild Hunt
  13. Bewitched Knight
  14. Splinter of Imperium
  15. The Green Knight
  16. Displaced djinn
  17. Servant of Steel
  18. Diminished god
  19. Dragon
  20. Death  

As a note, this is entirely based off of a footnote in Susanna Clarke’s Jonathan Strange & Mr. Norrell