So it sounds like the Zhents is the first confirmed course of action (possibly followed by Harpers or Emerald Enclave. Though interestingly Emerald Enclave are not on the list for getting a cleric to speak with the dead. But Harpers and Zhent are both on it). 

Those who wish to see the Zhents arrive at the Yawning Portal and are able to meet with Davil. As he did last time, he buys you a drink and lets you lead the conversation.

At the mansion, Oriace listens to Mana’s rapid-fire deductions with a thoughtful nod. He takes a moment to consider before offering an alternative theory. “Maybe the gnome was in the sewers and stole something from the Xanathar, and that’s why he was being hunted. Maybe the Zhents were pursuing him, or maybe they were protecting him. He could have been working for any faction—or none at all. But someone wanted him dead, badly enough to kill everyone around him in broad daylight.”

He sighs, shaking his head. “And for some reason, he was heading to us.”  Glancing at the others, he adds, “I’m glad you’re coming, Mana. Anyone else?” 

With that, Oriace leaves for the Yawning Portal, making his way through the familiar, boisterous crowd to find Davil Starsong. Oriace takes his drink but doesn’t waste time with pleasantries. “We saw an attack this morning—a fireball in Trollskull Alley. Killed eleven, right in front of our tavern. And I identified one of the bodies as a Zhent—a fact I have been withholding from the watch so far.” He leans in slightly, voice lowering. “It seems like the target was a gnome. The strange part? He was moving toward our tavern. Not sure if he was being pursued or protected by the Zhent—but he had spent time in the sewers recently. Could mean a connection to Xanathar’s people, though whether he was with them or against them, I can’t say.” 

He meets Davil’s eyes. “You can probably guess why we’re here. This explosion happened on our doorstep. We want to know who had the audacity to make such a move in broad daylight—and why. If the Zhents are already looking into this—and I cannot fathom why they wouldn't—we’d rather be ahead of it than caught in the dark again.” He taps a finger on the table. “A spectacle like that isn’t exactly good for business. Is there anything you can tell us, or do for us?”

"News travels fast in Waterdeep. I have heard of the fireball, and it really is dreadful. Two of the bodies in fact had tattoos of the Zhents. That was discovered fairly quickly in the morgue. The description our spies reported do not match anyone that me or the rest of the Black Network know of, so they must be part of the other branch of Zhentarim here. If so, I can't say I am sorry they died, though if the fireball was related to them or Xanathar, it won't help our cause for a legitimate economic foothold. If the gnome was trying to reach you, it sounds like you have managed to get yourself involved in something big. No one causes that much destruction over something small. It sounds to me that those "Zhents" (complete with air quotes, showing how he truly feels about the other group that call themselves Zhentarim) and a third party with someone powerful enough to produce a fireball, were both trying to stop the gnome from reaching you. As for why he wanted your tavern, maybe it was just that the tavern was somewhere he counted safe? Maybe he knew you without you knowing him? Only he knows that. 

Our spies have yet to report any progress from the Watch yet. And we are not spending any resources actively investigating further at the moment as we had no real need. Seeing as there were dead Zhent's chasing a gnome, the Watch are not blaming us for the fireball, and so we do not need to prove our innocence. Additionally, they are not suspicious of you. They don't believe you would set off a fireball so close to your own property. That being said, if you have anything you would like us to investigate, I could see what I can do."

Oriace nods, taking in the information Davil shares, and sighs dramatically. "A damn shame, really. Would’ve been ideal to hear the gnome’s version of events before he was silenced so thoroughly. But alas—" he leans back, swirling his drink absentmindedly, "—I’m not quite ready to take a stroll down the River Styx just to catch up with him, not for that at least." He lets the statement linger, watching Davil’s reaction carefully. 

"But I do agree with you," he continues, setting his cup down. "No one burns that many people alive for something small. It must have been important. And, interestingly enough, I heard there were actually three Zhents in pursuit of the gnome—yet only two ended up dead." He lifts an eyebrow. "The last one got away after taking something from the gnome’s body. Which means—" he gestures lazily, "—it would seem your... rivals now have an edge." He watches Davil carefully, letting the implication settle.

"Now, I understand your position, Davil. You're not spending resources on this mess, because you don’t need to. The Watch isn’t breathing down your neck, and it’s not your problem." Oriace tilts his head slightly, voice lowering. "But if we look into this, and it just so happens to hurt the other branch of Zhentarim, wouldn’t that be something worth knowing? A third party just pulled off a blatant, magical assassination on the streets of Waterdeep, and your rivals were tangled up in it."  Oriace leans in, a small smirk playing at the edge of his lips. "Wouldn’t you love to know what they were after? Because we would, too. And if we were, say, doing this for you, well... I imagine you'd find a way to help us, wouldn't you?"

Wagner suggests to his fellows (if anyone else joined the Harper’s) that touching in with them might be a good idea.

[[I’m drawing a blank on who my Harper contacts are and how to meet them.]]

Sterling nodded at Wagner's suggestion. "They're supposed to be the good guys, helping out the community and all that. Well, this trouble was laid at the doorstep of our community, so I would think they'd have an interest in seeing it dealt with. What say we give Mirt a visit and see what he thinks of all this?"

(( Sterling is ready to go, although aside from the theater I also don't recall exactly where Mirt can be found. ))

"The ball is in your court Oriace. I have offered my assistance if you have something particular in mind. But I am not a blank cheque. I will endeavour to be as direct with the investigation as you are with me. If you are vague, then the assistance will be vague. If you ask for something explicitly, I will respond likewise. Now this isn't a guarantee of help. If you ask me to break into the Open Lord's abode, I will quite bluntly tell you how futile that is. But if you know the name of someone, or a feature that makes them stand out, and you want to find where they are, that sort of thing is of no trouble. I will tell you now though, your mystery third Zhent is currently untraceable. We simply do not have enough information on them. For all we know, they are drinking at a table in here and none of us would even know."

(Harpers contact is Mirt (can't remember his surname currently). He has a property that you have the address for. But he isn't always in so sometimes its a waiting game)

Toser chooses not to visit the Zhents.  "I will seek out Mirt, he has a manor in the Sea Ward. He is the contact for the Harpers. I will go and ask what they have heard about the explosion and what other big things might be afoot that someone would do such a thing openly in Waterdeep.  I do not know this city that well, but it seems law and order are paramount."  

“I think the three of us should go, I’m a little concerned for our safety until we get more of a handle on this.”

The three? of you left go to find Mirt. Despite him telling you that if you ever need to speak with him directly, you are welcome to visit his manor in the Sea Ward, actually getting hold of him is hard. (If the characters do visit Mirt’s manor, there’s a 90 percent chance that Mirt isn’t home and no one answers the door). But if you are willing to just wait around he will eventually turn up. 

Mana finally chimes in.

”Davil, can you put us in touch with someone who has access to the bodies and has the magic to glean information out of them? I’ve never seen it done, but it is rumored that the dead can be called back temporarily to answer questions. We could formulate a list of questions for the gnome and perhaps one of the “Zhents” and decipher each of their motives. This would certainly go far in determining if this is a thread worth pulling or if it is an unprofitable distraction.”

“We can try waiting in shifts… gives us each a 1/3 chance to be the speaker.”

"All it takes to get someone a cleric to go speak with the deceased is the right sized donation to their temple. We can cover that cost for you, and an additional amount to ensure their confidentiality from any party who might be involved in this plot. Don't expect this to come without a favour on your part though. Expect to hear from me in the next couple of nights. You may give me up to 10 questions, 5 for the gnome, 5 for a "Zhent" and once we have answers, I'll pass them back to you."

Quote from Charwoman_Gene >>

“We can try waiting in shifts… gives us each a 1/3 chance to be the speaker.”

"I'm fine with that," Sterling said. "It'll give me time to see what the leatherworkers and tailors in this part of the city are selling. I'll take the second first shift."

(( Edited to reflect fact that the shift roll was for #2, Toser ))

Oriace is caught off guard by how effortlessly Davil arranges the Speak with Dead ritual, and even more so by the Zhent’s willingness to foot the bill. He keeps his expression neutral, filing away the information for later, but a flicker of intrigue plays behind his sharp eyes. He takes a slow sip of his drink, then leans forward, fingers tapping lightly against the tabletop as he begins to carefully formulate the questions.

For the gnome:

1. What is your name?
2. To whom were you on your way?
3. What did you want to ask them?
4. What did you do in the sewers?
5. Who, besides the Zhentarim, pursued you?

For the dead Zhent:

1. What are the names of your two associates that pursued the gnome with you?
2. What did you want from the gnome?
3. If you had been successful in taking what you wanted, where would you have brought it?
4. What is your factions disagreement with the Xanathar about?
5. ...

Oriace pauses, rolling the fifth unasked question in his mind. He turns his gaze to Mana, who has been following the conversation with the same focused intensity. "What do you think?" he asks, voice lowered just enough to keep the discussion between them. "Are these precise enough? Would you change anything? And more importantly—what’s our last question for the Zhent?"

We are of like mind, Oriace. My questions would be very similar. Do we need to present the questions now? Or would it be better to brainstorm with our whole troupe and return with a consensus grouping?  Here’s what came to my mind:

For a deceased Zhent:
What do you know about the gnome you were following on your last day?
What guild or faction hired you to follow the gnome?
What were your complete instructions about following the gnome?
What item did the gnome carry that could not be left with him?
What is everything you know about that item?

To the departed Gnome:
What guild or faction were you representing in your last moments of life?
Why were you going to the Trollskull Manor?
What item were you carrying that was more important than the gems you carried?
What is everything you know about that item?
Who are the top three groups that wouldn’t have wanted you to reach the Manor?”

Oriace nods thoughtfully at Mana’s suggestions, appreciating the sharper focus on the item the gnome carried. He drums his fingers lightly on the table, considering the best course of action before turning to Davil. “I agree with Mana—these questions are important, and we should be precise. Would you prefer we finalize them now, or can we take a short time to deliberate with our companions and send them to you by messenger?” He glances at the Zhentarim agent, gauging whether time or efficiency is more important in this exchange.

"The sooner we get them, the sooner we can ask them. But if you want to discuss first you may. What would work is if you have them written down by tonight, I will send a messenger to the manor to pick them up, and probably drop off a note with a favour you could do for us in exchange. One of my fellow Doom Raiders will have something they could have assistance for I am sure so I will discuss with them before this evening. The messenger will be of the same sort as when we first contacted you. Leave a window open."

Jumping to the Harpers.

Mirt turns up during Toser's watch, ready to hear what you are looking for him for.

Oriace gives Davil a small, appreciative nod. “That arrangement suits us well. You have my thanks for your assistance. We’ll have the questions prepared by tonight and leave a window open as instructed.” With that, he downs the last sip of his drink and stands, motioning to Mana. “Let’s get back. The others should have their say before we finalize anything.”