Close, when a Naaru or Void Lord’s energy is spent they are supposed to swap. We saw this with three(?) Naaru, the Blood Knight one in Sunwell, the Dark Star in Shadowmoon that Velen sused out of their ship, and the other Orc faith one that happened to be another deity the Draenei just let suffer in Nagrand.
I guess there was also that one in the Legion dungeon…
Also when a Prime Naaru dies a horrible curse is brought to the universe, they inflict borrowed power on the hero. u.u
There’s another we can kill in Maldraxxus as one of the Gladiators.
You’re not alone I also thought that when a naaru dies it inverts to Void then back to light when slain as a void naaru. I thought they were part of a never ending cycle but I guess that…idea does go out the window with how Xera got blown up in Legion and her child disintegrated by the legion
From the Uuna questline, the Naaru actually have their own realm where they welcome souls.
… Although that wasn’t established much in the Shadowlands expansion, merely with some vague mentioning – and even then, could’ve been seen as obscure.
Alexandros Mograine says:
“But why was I not chosen? Was my faith in the Light not strong enough? Was my soul tainted from the moment I rose into undeath?”
Xandria says:
“Light, Void… such trifling powers have no purchase here.”
However:
Keep in mind ‘The First Ones’ could had built the Shadowlands & structured its ordering system to keep order & stop chaos from unfolding.
Perhaps souls use to go to their respective realms accordingly, however could slip back into the physical realm when the living resided as ghosts, spectres or those seeking power?
Souls ‘destroyed’ in the Shadowlands could had perhaps just merely been dispersed until eventually reforming & being able to continue their ambitions once more.
The Shadowlands may perhaps just be an inbetween realm created by the First Ones between the phsycal realm and the true afterlife, like a protective barrier dam … Preventing the higher possibilities of necromancy, liches and undeath from being a greater threat to the rest of the cosmos – such would give a little more explanation into the powers of the Drust (able to pierce that veil into their own realm).
I’d wager like many cosmic beings, when Naaru die – If untainted, they return to their spirits return to their own cosmic order plane. 
If the being in question has been too heavily touched or altered by another realm though (eg. Z’rali) , that’s another mystery … Perhaps they reincarnate as a mortal with an affinity to one or the other? 
That could open up some cool storylines & interesting new characters.
Ok that made me laugh lol
That’s not true. You can always nit pick and find errors but often times there are explanations. For the most part SL was pretty straight forward.
It is true.
Anyone who argues Shadowlands is ‘Straight forward’ or “wasn’t that bad” is just rolling along with the echo chamber of the minority crowd who somehow liked it.
Not an point you can make with a rational argument. It was a typical afterlife that fit within the scope of a video game. They had Kyrian to carry souls across to SL (i.e. Angels), they were judged by an arbiter (like St Peter), and they had zones very much like typical afterlife zones for good (Ardenweald), reforming (Revendreth) and evil (the Maw) each ruled by someone similar to what you see in other religions.
So how was it not straight forward?
The concept was straight forward
But the story and the way Blizzard explained it and how it worked was a hot mess express with a dumpster fire on the side.
They tried to do a multi-mythological afterlife and kinda dropped the ball on all of it. Revendreth was supposed to be a sort of Purgatory, but Korthia was… a mish mash. And Maldraxxus was supposed to be a Valhalla - but they missed out on the golden halls and went with rot? And Ardenweald was supposed to be Elysian planes but missed everything. And Kyrian was Elysian planes and Valhalla poorly mixed.
Edit: Actually I have no idea what the Shadowlands were aiming for and I study a lot of ancient religions and I’m still confused what they were going for. Korthia was suppose to be the library of the aetheric pillars of wisdom, whatever they made it into, it was not that.
I’ve seen several rational arguments throughout the forums referenced to you, and you dispute every single one of them in absolute denial.
What a copout lie.
Not to mention it ignored & threw up heaps of established lore of what had been established about the Shadowlands already – and souls in general, throughout the history of WoW - right out the window …
It ignored the source-material of its own platform. I’m not going to sit here & list them, because I’ve seen you demand such before, others do it before only for the outcome of which to you shunning or casting them aside as no big deal. If you want detail to how, watch one of the countless videos on it.
… As I’ve seen Tovi once say:
If most players in-game, on the WoW forums, non-WoW forums, streaming services such as youtube & twitch along with multiple various social media outlets all majorly share the opinion that most of it sucked — Maybe, just maybe - It sucked. 
Getting out the gloves.
Sure you can say that and it sounds clever but that’s just your opinion. It’s not a proven fact and there is no solid evidence that a majority of players felt that way. Yes there was a very vocal minority of people in this forum and others that hated SL but forums in general represent a minority of players so it’s a minority within a minority.
Fact is the anti SL crowd does NOT speak for “the players” as they claim they do. We just have no idea how “the community” felt about Shadowlands.
Very well put, and I can understand how people would feel that way. But to me the Maw was far better than Dante Alighieri’s Hell where he just had people sitting in rings. Revendreth was 1,000% better than Dante’s Purgatory with their sword fighters that were a cross between vampires and the Musketeers.
I loved the Winter Queen and the way she rolled her eyes over Elune who was prised so much by the Night Elves but she saw her as her bratty little sister. I loved the dry humor of the dregers and the Prince in Revendreth.
And all anyone can say is “the players” didn’t like SL because we say so.
Translation, when “my betters” tell me I’m wrong, I argue back. Talk about arrogance.
As for the bots, we still have not seen “the first ones”. So they created bots, it can be argued that we are biological bots created by a higher force. That would be the fundamental message of just about every major religion.
Where do you think Shinobi get those Shinigami for Dead Demon Consuming Seal. Joking… Naruto is just casually summoning Ichigo Kurosaki (I say casually, but considering the seal consumes the caster’s soul on use, I may be saying that ironically).
I think we mortals should be cautious thinking our little minds are even capable of holding a full picture of the complexity of the cosmos.
Spirits of different realms often return to those realms when their forms in our reality perish. Beyond that, we’d need to visit their realms to see more of their life cycle.
Even having visited the Shadowlands, I’m still not convinced we fully understand how the Shadowlands works. We never really explored it from the angle of “what happens to beings of death if they come to Azeroth and then perish” …. we were too focused on “what happens to us” (and what happens to wild gods since the realm of life has sort of outsourced its reincarnation)
If it dies it goes to the shadowlands like normal unless some other force stronger then the kyrian acts on it first, i think.
De other side being bwomsamdi’s while in the shadowlands justified all the little afterlives that had been mentioned separately (avianna’s bird after life comes to mind but theres others).
Odyn managed to get a death domain and an army of dead guys by just having some kyrian knock offs get there first, which lead to like 70% of all the keeper related problems on azeroth but he still managed it as just a keeper with some titan forged assistance.
The titans either hid in their keepers or on ordered planets(based on eonar in antorous) after sargeras killed them, but then denathrius forced a baby titan argus into the shadowlands when he died and that effectively nuked the arbiter.
Elune was keeping nightelves around as a whisps for 10000+ years on azeroth, this is something she reconfirmed in SL, she would have kept them when the tree burned but let them go cause she thought it would help ardeanweld.
Since Naaru are at least keeper tier for the light theyre probably grabbed by whatever the light pantheon is and reinfused back into wherever they originate when they actually die from non-void stuff.
I hope they elaborate on the flip flop though in the next couple expansions since they have a void theme its been vague since tbc and only got a little in legion but they can definitly fit it into the next couple expansions with how heavy the light vs void is gonna be.
Trolls get taken by Bwonsamdi / Muehzala… except then you find Zuljins soul in a hidden basement in Revendreth, so apparently some troll soukd do go through the normal process?
Shadowlands really was just so awful
They pretend that Shadowlands doesn’t exist, like we do. Like Blizzard does.
This is what I’ve gathered about naaru from in-game observations. If they die quickly and violently, they just shatter and cease to exist. If they die slowly, they transform into a void lord.