The fifth edition of Dungeons and Dragons seems like it's got a whole lot of longevity. Wizards of the Coast keeps releasing new sourcebooks for this version of the game, and so far, it's been a long list of hits. Wizards is using the Dungeons and Dragons IP wisely, too, by not sticking to the beaten path. It's done some very successful crossovers with Magic: The Gathering and Critical Role, and there's bound to be more of the same kind in the future. It's also found a lot of good themes for expansions. Next May, Wizards of the Coast will be releasing Van Richten's Guide to Ravenloft, a book full of horrifying monsters, races, and subclasses themed after dark magic.
Van Richten's Guide to Ravenloft sounds like it'll have a lot to contribute to Dungeons and Dragons. However, it continues the pattern of Wizards of the Coast occasionally returning to familiar territory when not doing ambitious crossovers. After all, Curse of Strahd already gave players a taste of Ravenloft. Dungeons and Dragons has a huge multiverse of campaign settings only explored modestly in sequels to the Monster Manual, like Mordenkainen's Tome of Foes.
It would be great to see some expansions focused on some of the more far-out reaches of the multiverse. There's tons of Dungeons and Dragons planes that would be rich sources of monsters, subclasses, races, magic items, and more.
Dungeons and Dragons: The Feywild
Wizards of the Coast loves making references to the Feywild. There's subclasses related to fey magic for every class, from bards to warlocks, emphasizing the importance of this mysterious and whimsical plane. A sourcebook all about exploring the Feywild would be great. It would give Wizards of the Coast the opportunity to come up with fey-inspired subclasses for classes like monks and rogues that haven't crossed over with the plane yet.
It'd also be a good opportunity to reprint playable races like satyrs and centaurs for Dungeons and Dragons players who don't want to invest in the Magic themed books. Dungeons and Dragons could really use more fey enemies, too. If such a sourcebook came out with some enticing magic items on top, it'd be a really valuable book.
The Nine Hells and the Abyss
These two regions have been explored a little more extensively by the Dungeons and Dragons developers. Mordenkainen's Tome and Volo's Guide to Monsters both vastly expanded on the game's repertoire of demons and devils, and there's adventure books like Out of the Abyss that explore these realms. However, the planes of fiends make such a clear and present setting for high level adventures. It would be great to see a sourcebook that fleshes out these planes more fully and gives DMs inspiration for adventures in this wretched realms.
It would be great to see a demon empowered barbarian class, too, or even a special wizard class specializing in profane devil's magic. The Nine Hells and the Abyss are bound to be full of magic items that no mortal adventurer is ever meant to find -- which makes them all the more worth finding.
Mount Celestia
Mount Celestia is only described briefly in the Dungeon Master's Guide, but it's clearly an important location. This is an extremely magical and restful place where heroes and angels reside. Although it sounds like a very safe place, its denizens are apparently ever on guard for attacks from evil forces, so there's still room for adventures here. Just like fey, Dungeons and Dragons could use more celestial stat blocks, and there's no better source for those than Mount Celestia.
It'd also be a great excuse to come up with magic items and other permanent boons that gods and angels might bestow on adventurers for heroic deeds. There's room for more celestial themed classes, too; it'd be a good reason to revisit the Theurgy wizard subclass that made waves in the community when it emerged as Unearthed Arcana.
Ysgard
A less important lane in the known multiverse of Dungeons and Dragons is the world of Ysgard. This is a place of endless war, full of conflict and endless heroic deeds. Ysgard might not have the kind of cosmic implications that the Feywild or the Nine Hells do, but it's a rich opportunity for Dungeons and Dragons adventures. For instance, this plane is supposed to be full of giants. It'd be a great opportunity to add more giant stat blocks. Wizards could also riff off of Tasha's Cauldron of Everything's Rune Knight subclass and make a giant-themed paladin or barbarian subclass.
On top of giant themes, an Ysgard sourcebook could add more dragon stat blocks, all kinds of humanoid NPC stats, and even some tips and tricks for DMs to spice up combat in any campaign. Lots of books suggest puzzles and traps for DMs, but some ideas for special fight mechanics might draw the eye of veteran Dungeons and Dragons fans.
The Astral Plane
Although all of these planes can make great adventures possible, the Astral Plane shines brightly as an intersection of all these planes and more. This is the mysterious psychic world where travelers from all planes come in search of gateways to other planes. Dungeons and Dragons has already touched on the lives of the githyanki and githzerai and made them playable, but they're only one factor of the Astral Plane.
If Wizards of the Coast doesn't want to focus on any one of these worlds, the Astral Plane gives it the chance to introduce more stat blocks from all over the multiverse. At the same time, a sourcebook from this gateway plane could offer magic items and spells meant to represent lost knowledge floating around the Astral Plane that players can rediscover.
Dungeons and Dragons 5th edition doesn't look like it's going anywhere anytime soon. This is probably the most popular that this TTRPG has ever been. Wizards of the Coast only has reason to keep investing in it, rather than trying to replace it. As long as this edition of the game is doing well, the developers would be wise to diversify. There's a lot of aspects of the game's setting that Wizards has yet to explore. It already has a rich setting on its hands; it's just a matter of putting a foot forward and capitalizing on it.
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