So imagine a board meeting in the Nine Hells. Each of the Lords of the Fallen steps up to give their quarterly report, summarizing the souls they've reaped and the evil they've sown in the multiverse. Each fiend in turn lists the blasphemies and atrocities they've unleashed and the good beings they've led down the road to wickedness, each new testimony a fresh litany of horrors. But of course, it's all just a prelude to the main event, as Asmodeus himself steps forth the address the crowd.
"My evil brethren," he smiles, "my greatest scheme has come to fruition. I, the Prince of Lies, have corrupted the powerful Cassalanter family of Waterdeep!"
Belial, Archdevil of Phlegethos, laughs a bit nervously. "Ahh, my liege, but don't they already worship you? They built a shrine in their basement, after all..."
"Yes, but I offered them wealth and power!"
"Ok, but they kinda already had that."
"Ahh, but you're missing the best part of my plan! You see, I've tricked them into signing away their children's souls!"
Dispater hesitantly raises a clawed finger. "I'm not sure that's how souls work, my liege.."
"And in order to get out of the deal, they must provide me with ...very nearly a million gold coins!"
"Got plenty of those!" Mammon chimes from the back.
"And they must corrupt themselves by slaying 99 innocent people!"
Fierna flicks her tail dismissively. "...whose souls I'm pretty sure we don't get, Milord."
"Yeah, and the Cassalanters are already pretty corrupt. They do kinda worship you and all..." Belial offers.
Asmodeus allows himself a grin. "My lords of evil, as always you underestimate me. You fail to see the brilliance of my master stroke of evil. You see, if the Cassalanters fail to meet my terms- and there's at least a 50/50 possibility that they might- I shall turn their two remaining children into... two...very nearly deadly...LEMURES!"
Ok, you get the point. I'm a big fan of Waterdeep: Dragon Heist, but the whole Cassalanter storyline has some issues. No one's motivations make a lot of sense- the Cassalanters don't noticeably gain more or success than other Waterdhavian NPCs the players meet, and to avoid the consequences they have to give Asmodeus money and innocent souls, two things he doesn't need. The culmination of Asmodeus'master plan is the corruption of two people who already worship him and the transformation of their two children into devils that on a good day might inconvenience an asthmatic kobold.
The worst part of all this is that this whole scheme is the way the players get railroaded into a Trolley Dilemma. It's easy to see how this idea looked great on paper, but in practice Trolley Dilemmas suck to live through- that's exactly why it's a fascinating intellectual problem, because you imagine what it would be like to have to make that choice, safe in the knowledge you don't actually have to face it. As a role-playing plot point, it's completely unsatisfying.
It's also very possible that the players won't get to make that choice at all- that they'll only find out the consequences of their victory over the Cassalanters after the fact. Unless the DM is very diligent about putting clues in the players' faces, there's nothing inherent in the plot that's going to make it clear they're facing a Trolley Dilemma in the first place. The players get the trauma of tough consequences, but that pain could very well be unearned.
So the Trolley Dilemma sucks, and the backstory propping it up is steaming trash. OK, now I'm going to suggest a simple way to fix it. It's a minor change, but works so much better I'm kinda gobsmacked that the authors didn't do this in the first place.
Here's the secret sauce:
ASMODEUS' PLAN IS TO GET THE PARTY WORKING FOR HIM
That's it. You can do everything the same way as its' written in the book, but just change Asmodeus' motivation. Assume he's taken an interest in the party, and wants to see if they can be useful to him. So he engineers this whole scheme, putting the party and his pawns the Cassalanters on a collision course over the gold in the vault, as a bit of a test. If the Cassalanters outfox the party and get the gold first, then the party has failed and Asmodeus has no use for them- he gets to enjoy the satisfaction of the party learning that their failure led to the deaths of 99 people, because, you know, evil.
But if the party succeeds, Asmodeus knows they're destined for greater things, and that's when his master plan actually starts to look like a master plan. He takes the Cassalanter kids as written, maybe turns them into Lemures just like the book says, and he makes sure the party knows that it was the consequence of their victory over the Cassalanters. Asmodeus lets them feel bad for a bit, before he gets a message to the party: "You guys seem pretty broken up about what happened to those poor, innocent kids. Of course, there's nothing in the contract that says I can't restore the children to their mortal bodies, in exchange for a few small errands..."
Here's what that gets you:
- Plot Hooks Aplenty. Now you've got the party in hock to the biggest baddie in the Multiverse, who could plausibly send the party anywhere to do anything. Of course, they'll want to find a way out of Asmodeus' clutches, which could lead to all sorts of side quests. Instead of a dead-end, now you've got all sorts of opportunities.
- A Party-Centric Story. It's not about the Cassalanters and their backstory anymore- now what's driving the action is centered on the characters.
- The Players Get A Way To Save The Kids. Because the Trolley Dilemma sucks, and having them send kids' souls to Hell because they stopped Devil worshipers from winning is garbage.
- Asmodeus Seems Smart Again. The end game is NEVER lemures.
BTW, this was something I incorporated into my supplement to Dragon Heist on the DM's Guild,
Cruel Summer, which adds a whole additional angle to the Cassalanters' story with some new locations, a demonic faction and a mystery to solve, because if there's one thing Dragon Heist needs, it's more complexity. But the party does get a chance to rescue the kids and re-negotiate the deal with Asmodeus, so there's that.