Mordenkainen Presents: Monsters of the Multiverse is a new Dungeons & Dragons book that features revised versions of over two hundred monsters in the game. The Demon Lords have received an unusual change, as the madness effect that was inflicted by their lairs has been removed from the game. Now, a far weaker effect has been put in its place.
In the lore of D&D, the Demon Lords rule over the Abyss. Like the Archdevils that rule Baator, the Demon Lords are incredibly powerful and are about as close to being divine creatures without actually being gods. It's fortunate for the rest of the multiverse that demons and devils despise each other, and have been waging the Blood War against each other since the beginning of creation. If the fiends joined together, then the Prime Material Plane would be ripe for invasion from the combined hordes of hell.
The commanders of the demons in the Blood War are the Demon Lords, many of whom have appeared as antagonists in D&D campaigns. Many of the Demon Lords were statted out in a book called Mordenkainen's Tome of Foes. These same Demon Lords have been updated in Monsters of the Multiverse, which is available now as part of the D&D Rules Expansion Gift Set. The Demon Lords have lost a notable power in Monsters of the Multiverse, which is likely a result of sweeping changes that have been happening in the game.
Demon Lord Lair Action's Related To Madness Were Cut In D&D
In Tome of Foes, the Demon Lords Baphomet, Demogorgon, Fraz-Urb'Luu, Graz'zt, Jubilex, Orcus, Yeenoghu, and Zuggtmoy have a regional effect that is tied to their Lair Actions. To use Baphomet as an example; if a humanoid spends an hour within one mile of Baphomet's lair, they must make a DC 18 Wisdom saving throw against the Madness of Baphomet effect. If they fail the saving throw, then the DM rolls a d100 to determine the effect. What's interesting about all of the Demon Lord madness effects is that they are all roleplaying changes and not mechanical ones. The Madness of Baphomet has the potential to make a party member consumed with rage, act like a wild beast, and hunt others as if they were animals.
Although Monsters of the Multiverse makes some races stronger, all of the madness regional effects have been cut and some of them have far weaker effects, where a character has disadvantage on certain skill checks. It's likely that the reason these have been cut is due to their depictions of mental disorders. There are also some players who might not be comfortable acting out situations where their character has their personality changed in such a negative way.
There are other instances in the book where references to mind-altering effects have been changed, such as Amnizu's Poison Mind ability being renamed Blinding Rot. There was also a similar change in the errata for Tomb of Annihilation, where Mad Monkey Fever was renamed Blue Mist Fever. It's likely that Wizards of the Coast wants to remove certain words from its books going forward, as part of the changes to the lore of Dungeons & Dragons that have been happening over the past few years.
Mordenkainen Presents: Monsters of the Multiverse is available now as part of the D&D Rules Expansion Gift Set and will receive a standalone release on May 17, 2022.