http://keith-baker.com/eberron-flashback-the-lords-of-dust/
http://keith-baker.com/age-of-demons/
https://keith-baker.com/dm-overlords-2022/
Q: What are your thoughts on hellfire weapons, lemures, and the River Styx?
The principle of Hellfire Weapons is that they catch the souls of creatures killed by them and turn them into lemures on the River Styx, where they are recruited to fight in the Blood War. Eberron doesn’t have the River Styx or the Blood War. So what’s the point of Hellfire Weapons? Off the top of my head, I have three ideas.
One option is to tie them to Shavarath. Say that they’re tied to the Legion of Tyranny and that they catch souls and turn them into devils fighting for the Legion. There’s two aspects to this. Mortal souls ALREADY fight in Shavarath. Every mortal projects a conscript into Shavarath, the same way you project a dream self into Dal Quor when you dream. In this very moment, you ARE fighting in the Eternal Battleground. Which makes Hellfire Weapons slightly redundant. The catch is that your conscript-self is recruited by whichever Legion most closely matches your values and nature; the Hellfire weapon would catch your soul and force it into service for Tyranny. If I ran with this idea I’d make it an extremely new development likely initiated by a mortal: the immortals of Shavarath have been fighting their war since the dawn of creation and don’t do dramatic innovation. The idea would be that a mortal (Warlock? Artificer? Dragon? All of the above?) came up with this plan, theorizing that this would be a way to slowly but inexorably shift the balance of power in Shavarath.
Having said that, this isn’t an option I’d use. The whole point of Shavarath is that it’s AN ETERNAL BATTLE. Everyone comes back. It’s not really an interesting backdrop for a CAMPAIGN... and also, again, it's not really SUPPOSED to be a situation driven by dramatic shifts.
Which brings us to option two. What I’d do is to keep the core idea of the hellfire weapon—if it kills you, you are reborn as a devil in a hellscape, stripped of memory and forced to fight—and dump the part where the battle takes place in another plane. That’s right: I’d say that hellfire weapons are manufactured by the Lords of Dust, and you don’t return to the River Styx, you return in THE DEMON WASTES. I’d say that this was a recent breakthrough in Ashtakala—facilitated by Hektula and Sul Khatesh—and that Rak Tulkhesh and, say, Eldrantulku are recruiting forces into the Demon Wastes in this way. In theory they are going to raise a vast army of corrupted mortal souls and roll over the Ghaash’kala and into Western Khorvaire… but for now, they’re mainly fighting each other. So as a campaign, you get killed with a hellfire weapon and find yourself as a lemure in the Demon Wastes, assigned to fight alongside one of the Carrion Tribes against rival Carrions.
A third option, if you like that idea but want the battleground to be even MORE exotic than the Demon Wastes, would be to say that the weapons are forged by Mordakhesh and send your soul to the Bitter Shield, the heart demiplane of Rak Tulkhesh, which is another realm of endless war. In theory, again, Rak is building up a massive horde of soul-soldiers who will on day emerge to terrify Eberron, but in the meantime you are in a realm that is the heart of an overlord of war. There could be a river of blood there where you wash up that washes away memory, filling the Styx role.
Anyhow, there's things I might do with it! And in case it’s not obvious, in all of these cases the soul is being diverted from its proper path—Dolurrh and whatever lies beyond. So it's possible the Queen of the Dead might eventually take an interest once this hits a critical mass...
Q: If most of the Overlords remain true to their Speakers, were Mordakesh, Durastoran, and company already in their post during the Age of Demons?
The Prakhutu of the Lords of Dust are powerful beings that have a direct connection to an overlord. They didn't serve in these positions during the Age of Demons, for two reasons. First, the overlords didn't NEED Speakers during the Age of Demons, because they were FREE. They spoke with their own voices, and those voices could shake the world. "Prakhutu" wasn't a recognized voice. Every overlord had powerful fiends that were closely tied to it. Mordakhesh, for example, was always a commander of fiendish forces; he embodies the idea of the cruel general. But Rak Tulkhesh had OTHER mighty fiends in his service -- many of them more powerful than Mordakhesh. It was only after the overlords and their mightiest servants were bound that the overlords NEEDED someone to speak for them—only then that they establish that bond with the strongest of their unbound servants.
So: "Prakhutu" wasn't a role during the Age of Demons. The native fiends that are prakhutu today were all significant entities in the Age of Demons who served their warlords in some capacity, but they were neither their most powerful or most important servants. And should a prakhutu somehow be destroyed or just fall from favor, the overlord will form a bond with a new one -- as we've seen with Korliac of the Gray Flame.
In my conversion for the Savage Tide, I specifically suggest using Demogorgon as a great lieutenant of one of the overlords who's managed to break somewhat free of the Flame. The point being that Demogorgon is significantly more powerful than the typical prakhutu, but also significantly LESS powerful than one of the overlords, at least as they were defined in the 3.5 rules.
Source: June 2024 Q&A