Traces in the Dark

It looks like all criteria for Traces in the Dark need to be completed on one character in order for this quest to appear, even though the achievement is warband shared progress. You can use this string to check your character's completion progress for the 4 quest item drops (Torn Twilight Missive, Halhadar Battery Core, Enchanted Naga Scroll, and Permafrosted Keystone)

/run print(C_QuestLog.IsQuestFlaggedCompleted(95069))
/run print(C_QuestLog.IsQuestFlaggedCompleted(94920))
/run print(C_QuestLog.IsQuestFlaggedCompleted(95071))
/run print(C_QuestLog.IsQuestFlaggedCompleted(95070))

This quest, as well as the four that lead up to it, serve as a teaser for the next phase of Void Assaults, coming in 12.0.7.

Here's what Maella has to say when you approach her:

<Riftblade Maella nods as you approach, gesturing you away from Auric and the others nearby, her expression serious.>

Ah, <name>, good. I was hoping my message made it to you.

Player: You wanted to speak with me?

Our recent victories—your recent victories—against these void assaults are all the talk in the upper courts of the city.

The Regent Lord, the Grand Magister, and the Ranger General have all expressed their gratitude for what you've done for these lands.

Magister Umbric, while no less appreciative, has taken your discoveries on the Twilight Cultists and is pursuing his own leads.

In the meanwhile, he has instructed me to chase down these void and ethereal threats and cut them off at the source.

And thanks to you, I have a lead of my own.

Player: What's your plan? I'm all ears.

I believe the dark particles you've brought to Mayven and Maren and the items you've found may be the key to our next move.

Remember that ethereal battery core you brought to the lightforged? One of their officers has reached out with some valuable intel on the Hal'hadar.

And Decimus hasn't stopped prattling about that keystone you brought him and Belath. He seems obsessively interested in where it leads.

My Locus Researchers have been working with Decimus to reverse the particles’ points of origin and... well, the rest doesn't matter until we solve that.

For now, continue pushing back these assaults. I will call on you when I have news.

Player: What about the Deeplurk naga at Daggerspine Point?

I have spoken with Aethas about the missive you found.

Eversong's coastal settlements have been placed on higher alert while these ritual sites are still active.

My growing concern is the evidence of the Hal'hadar ethereals trading with these “Deeplurk.”

The weapons they wield and the captured void entities my scouts have spotted lead me to believe the Hal'hadar have offered... something to the naga.

Fortunately, their smaller numbers are of less concern compared to the other threats.

Aethas's magisters and the shal'dorei stationed nearby will continue to monitor their movements.

The fact that you have to get all items for this quest to appear on one character is so stupid. The achievement is account wide, why would they make this quest character specific. Surely that would be a mistake, but this is one of those things that Blizzard will probably never fix.