After Greyhawk, the entire cosmology of inner and outer planes is secretly the second campaign setting in the D&D 2024 Dungeon Master's Guide
In the D&D 2024 Dungeon Master's Guide Cosmology chapter, game designer James Wyatt was given 32 pages of space. He used 39. Also this information moves from Chapter 2 in the 2014 5e DM's Guide to Chapter 6 in the 2024 DM's Guide. It's an excellent move because there's a lot to take in. Perhaps too much for the earliest chapters in any D&D book.
With Planescape being the literal hub for all things in the D&D Multiverse, Wyatt's goal was to make the Cosmology section more practical for use in adventures and adventure building.
Adventure Hooks:
Carceri Adventures – Adventures on Carceri might explore the forces—spiritual and psychological as well as physical and outright demonic—that keep characters trapped or imprisoned there.
A theme of imprisonment makes sense for that plane. You can't spell "incarceration" without "Carceri."
Acheron is "Where you go and you're told to fight and everybody fights because that's what you do there."
Acheron Adventures – A journey into Acheron is a confrontation with the bleak nihilism of unending conflict, the harsh reality of authoritarian rule, and the uncaring pressures of social conformity. It's also an opportunity for characters to grapple with the question of what they are fighting for, among armies that have forgotten how to even ask the question.
That's a heckuva paragraph. "Who wrote that?" Wyatt asks, because he wrote it. "That guy needs a raise or something."
The illustration of the planes' theoretical arrangement like a wheel around Sigil, the city at the center of the Multiverse, is excellent. They're not just a symbol and a name. Now there's a topographical tile to convey its material components. That's not easy to depict when you're given an alignment (like Chaotic Evil) and told to manifest it into something explorable for players (the Abyss). This illustration is identical to the one in the 2024 Player's Handbook, but the one in the DM's Guide adds the gate towns. Gate towns are what connect Sigil and the Outlands to their respective outer plane.
The Planescape: Adventures in the Multiverse slipcase set of books goes over all of this in greater depth.
There are lots of goodies to unearth. For example, the bottommost layer of Carceri is called Agathys. Black ice streaked with red covers this frigid realm. That's where the spell Armor of Agathys originated. But until now, no one D&D book connected those dots.
The 2024 DM's Guide didn't cook up all of this cosmology from scratch. The basis for a lot of this chapter comes from Jeff Grubb's AD&D Manual of the Planes from the '80s. Back then, the planes and their layers were lairs for all of D&D's pantheon of gods and demigods. "That is not a particularly useful perspective for the 5th Edition DM," Wyatt says, explaining why the Cosmology chapter is no longer just chart after chart of deities and demigods. Thank goodness.
What's the difference between the Inner Planes and the Outer Planes? The Inner Planes are the physical stuff that make up the Material Plane, which is where planets like the Forgotten Realms' Toril and Dragonlance's Krynn reside. Whereas the Outer Planes are where the gods live, playing out their existence in manifestations of thought and philosophy. Trippy.
As a Dungeon Master, this revamped Cosmology chapter is much more useful to me that the inclusion of hundreds of gods from dozens of pantheons. That endless family tree of deities never served me well in running games. But focusing on places for my players to explore, and adventure hooks to get them there, this is far more practical material for the hungry DM.
The D&D 2024 Dungeon Master's Guide is available everywhere you can buy D&D books on November 12.
