Hi all,

I have just started DMing an Eberron campaign on 5e. In the first session, the PCs started in a House Orien's train that had been sabotaged, going through the nation of Aundair. While underway, the train accelerated, the drivers lost control, the bounded elemental went mad... and an airship attacked. A mysterious wizard on the airship burst the locomotive's ceiling open using lightning magic, and a bunch of warforged boarded the locomotive to kidnap the driver. The PCs intervened, killed the wizard, routed the warforged who jumped ship, detached the locomotive from the rest of the train before it exploded and took control of the airship using grapnels set by the attacking commando. Upon finding the airship's driver (a member of House Lyrandar), they discovered he'd been subjected to mind control magic.

This action-heavy sequence was intended to give my players' the Eberron steampunk+swashbuckling feeling, as well as a reason to be together considering their characters' varied background. "You guys happened to be here at the right time and saved the day, now you're officially heroes, get a medal, and important people know of your skills... unless they want revenge from you."

However, the rest of the campaign shouldn't be as action-focused. It should revolve around espionage and cold war politics in the context of Eberron. Therefore, my players should feel entangled in the web of intrigue set by the various influential organizations of the setting.

So, here the synopsis as I envision it...

The attack was planed by House Tarkanan, the revived "guild" of aberrant dragonmarked bent on destroying mainstream Dragonmarked houses. Their plan was to intensify the existing rivalry between Lyrandar and Orien: after all, the former undermined the latter's dominance over transportation when airships were invented. Plus, Orien's lightning rails network was seriously damaged by the destruction of Cyre. So, Orien's resources are stretched and they're vulnerable to any unfortunate event letting people thing their trains are unsafe.

By organizing an attack that Lyrandar could be blamed for (because of the use of Lightning and Air magic by the wizard and of an airship), even if it was way too obvious, Tarkanan hoped to sow discord within the Twelve. Even if the Lyrandar baroness denies any involvement and generously provides Orien with financial aid to repair its damaged infrastructures, everyone knows how committed she's to expand Lyrandar's market share, and people could suspect anyway that a rogue faction that baroness can't control is acting from withing Lyrandar. Plus, it doesn't help that Queen Aurala effectively breached the edicts of Korth by granting Lyrandar rule over Stormhome, and seems to favor that house by frequently consorting with the ambitious baroness.

What's more, House Tarkanan, which isn't much more than a bunch of thugs on steroids for now, stroke an alliance with the Aurum. After all, they share the same goal: bringing down dragonmarked houses. The Aurum provides financial resources and political influence and Tarkanan brings striking power, while being able to mimick the powers of normal dragonmarks with their aberrant marks. For now, the Aurum has a good cover since the train accident cost a lot to some of its prominent members, as merchandise wagons were derailed.

Now, who's the mastermind? I'm considering Adal, the Queen's brother. He's very ambitious and dreams of replacing his sister as king of Aundair and, maybe, a unified Galifar. I could have him being a secret Aurum concordian. He could nurture plans for an absolute monarchy and therefore disapprove of Aurala's excessive generosity toward dragonmarked houses, thinking it undermines the monarchy. And he wouldn't be wrong at all. His position as Minister of Magic and connections in the Arcane Congress of Arcanix give him considerable resources.

Meanwhile, the Royal Eyes of Aundair will be on the lookout, trying to figure out what's going on. They may suspect foreign spies involvement. Undercover agents of Breland, Thrane or Karrnath might have unfortunate accidents. Diplomatic tensions would build up.

Besides, I sort of like the idea of a rogue Lyrandar faction too. Maybe Adal is in fact playing both sides. Doesn't he want to build new war weapons to use against Thrane? I'd very much like my campaign to feature a secret research facility where submarines are being developed. Or maybe improved airships for the military. Or both.

To complicate things, I could have a gang war going on in the underworld, with established criminal networks being challenged by Tarkanan and, to simplify matters, maybe Daask too.

Anyway, as you can see, I've a pretty clear plan of the overarching storyline. Yet, I'd like to know what you think about it. And, since I don't have much experience in preparing fully-fleshed campaigns (I so far have been DMing pre-made adventures or short scenarios I prepared myself), how would you have the intrigue unfold? Specifically, I would welcome advice on the following points:

1) Now that PCs are heroes, how would you bring them into the web of intrigue? I see the following possibilities:
-the Aurum takes notice of their skills and tries to have them work for it, one way or another. Remember, even dragonmarked PCs don't know what the organization is up to.
-the Royal Eyes takes notice of their skills and realizes they could be useful while providing deniability.
-the PCs are stalked by House Tarkanan, confronted by assassination teams, and forced to investigate the matter, for their own sake.
-the Twelve (the league of dragonmarked houses) hires them to investigate the situation. Normally that's House Medani's job, but likewise, they may want deniability.

2) What should their first adventures be? Once again, I was planning for two directions:
-investigations in Fairhaven's underworld
-a more standard mission, such as retrieving a magic item for some patron who happens to be either from the Royal Eyes (secretly), the Aurum (openly), or a dragonmarked house (secretly or openly). I could have two patrons compete for the PCs' help, forcing them to make a choice. Maybe PCs will face competition from one or more team of agents from other organizations. An initially straightforward mission may leave them deeply embroiled in the factions' powerplays.

3) At what pace should the story unfold ? By that, I mean, how fast should players understand what's going on? What sort of clues should they find, how many of them, how often? For example, I'm considering letting them find House Tarkanan's symbol, the dreaded beholder, on a trinket of some kind. They could be falsely led into investigating local Khyber cults, before realizing it was a dead trail (or maybe not). The way I see it, one of the more enthralling parts of such adventures is trying to determine who done it and what for. Once everything is known and time has come for an epic battle against the Villain, the story loses its appeal. However, players should still be fed enough information on a regular basis.

Regarding my players' backgrounds...
One, by far the most committed to storytelling and learning about the universe, plays a Gnome who's a secret agent of the Trust, posing as a journalist. Incidentally, he's also a warlock, having struck a pact with an entity from the plan of dreams, Dal Quor. This entity may be a malevolent servant of the Dreaming Dark or a good-aligned spirit, similar to those who bounded with Kalashtars. The Gnome doesn't know. Anyway, as an agent of the Trust, his goal should be to accumulate as much information as possible, preserve the geopolitical status quo, or steer it in a way that's favorable to Zilargo.
Then, we have a House Ghallanda cleric, a House Vadalis druid, and a veteran warforged forced to work as a guard due to the end of the Last War.
The former two could provide opportunities for more complex relations with the dragonmarked houses. House Vadalis in particular has strong connections with Aundair, as it's providing the dragonhawks used by its elite soldiers. But, anyway, their characters were created on the day of the session and aren't as developed as the Gnome.

Well, that's it. Thanks in advance for reading this wall of text and for your feedback!

[I'm not sure whether this forum is strictly about rules or also about storyline brainstorming involving 5e and D&D settings, so I asked this question in a much general tone on the General Discussion forum. Sorry for the inconvenience, if any.]