Just to clear some things up in no specific order:
The Light and the Void (which is also the Shadow, the font of all Shadow Magic) were the first forces (entities?) in the universe. It's literally the first line in the WoW Genesis myth:
"
It is said that in the beginning there was Light and there was Void and in a time long ago, the two collided in the abyss of the Great Dark. As a result, infinite worlds spiraled out into the newly forming cosmos"
All the gods, all the worlds, come after the collision of the Light and the Void,
within the Great Dark Beyond. The Great Dark Beyond is therefore space itself, and the consistency of it existing before the collision is unclear - however the Void is older than the Old Gods, therefore they did not create it. Shadowpriests and Old Gods alike
use Shadow/Void magic - we draw from the same font of power - but we do not draw from Old Gods themselves as a source of power.
This means we do not worship the Old Gods, but - perhaps - we at this point worship
The Void itself. In the same way that Holy Paladins worship The Light.
Priests, distinct from Holy Paladins (who denounce and deny the Void), acknowledge both Light and Shadow(Void) - but while Holy Priests specialize in mastery of the Light, Shadowpriests specialize in mastery of the Void.
In WoW, it's important to note that Priests are all
Psychic - we all have psychic power - and are the only class with any psychic ability. Shadowpriests in particular have many Mind-altering and Psychic spells than other priests: this suggests that connection to the Void may be related to Psychic power in WoW Lore.
This hypothesis is further supported by the association of all other Psychic lifeforms in WoW: namely, Old Gods, servants of Old Gods, Naaru, Forgotten Ones, and some shadow-related species like Mindbenders (ex. Throne of the Tides Mindbender boss).
All psychic creatures in WoW also wield Shadow magic in addition to their psychic power: this cannot be coincidence. Therefore, The Void is a psychic medium through which Shadow-attuned beings can communicate.
This means that all Shadowpriests can communicate psychically with one another - as we do on this forum
It also means that we share a psychic medium with some very powerful psychic entities. Old Gods. We chat.
We share a connection with the Old Gods, not one of master/slave as the Twilight Hammer experience, but as colleagues - sharing our mutual interest in The Void.
It stands to reason that prolonged exposure to the true nature of reality is beyond any sane comprehension - that it is our connection to The Void,
not the Old Gods, that is slowly driving us insane. It then stands to reason that the Old Gods themselves were not always insane either - it is their connection to The Void that drove them all insane.
That we Shadowpriests can touch madness - harness it for our own empowerment - and then return from that insanity unscathed when combat ends suggests that we
are retaining control over our own insanity somehow: lest it would never leave us - we can begin an Apotheosis into purely void-form, beyond even our shadow-form - and then
return.
Consider not the questionable choice to fondle that dangerous power, but question for a moment - that Shadowpriests alone can return from that place. Not only can we step
into the Shadows, but we can come out the other side. 46 and 2. Just ahead of me
Obligatory Tool:
In semi-related news, an interesting side-note to the talk of the Void / Great Dark Beyond / Old Gods, is Elune.
In Night Elven mythology, Elune (Azeroth's largest moon) is a literal god who created the world (Azeroth) with the aid of two other, never identified gods. Apparently in Suramar - which we will finally see in the Legion expansion - this is portrayed in murals on the walls: our oldest temple to Elune, and perhaps the oldest structure in Azeroth.
The Twilight's Hammer has a similar belief - that the Old Gods created Azeroth - and that the Titans were space invaders who later arrived at the already created and inhabited Azeroth. I had always assumed the Titans contested this belief, but in
The Sundering (book), the titans actually acknowledge that
Three Old Gods pre-dated their arrival at Azeroth.
I know a lot of Nelf fans who were terrified they were going to retcon Elune into a crystalline entity (Naaru) - but instead it seems perhaps Elune is an Old God? That'd be a weird twist.