To me, that WoJ implies that there are non-human guardians acting as wardens of Demonreach on the never never side. That is something I hadn't considered before and something that Harry should investigate, like, yesterday.
It is my opinion that when Harry descends down all those steps and enters the chamber down at the bottom, he has gone down the rabbit hole and in most respects *is* on the NN side of Demonreach.
I say in most respects because Demonreach was created and exists on a dimensional level that Harry has a hard time experiencing, so when he's down there his experience is kinda skimming the surface of a pond of what is actually there NN wise without necessarily getting wet.
I haven't followed this conversation closely, but let me share a little more of my opinion of who and what a capital "W" Warden is and why it is significant. As with most of my theorizing over the past few years, this is heavily influenced by my concepts of
overall DF cosmology, and the mortal experience's position in and influence over that cosmology.
The entirety of the Demonreach construct was created on and exists on a level that spans more than just Harry's individual reality and timeline. It is immense and powerful and enduring and ... Lithic. What do I mean by "Lithic?" It exists as is and is non-introspective and unchanging in its purpose, function, and resolve.
But on the Demonreach level of the big picture, the fabric of Reality has a degree of malleability, and the driver and medium of this malleability is mortals and their free will. For Demonreach to function on this malleable level of existence, it needs a malleability engine of its own. A Warden capital W, with free will who can make decisions that encompass aspects of its purpose that require more malleability, dynamism and introspection than it possesses on its own as a Lithic construct.
It is possible that Demonreach's existence is wide enough that it interfaces with more than one discrete "Capital W Warden" across multiple discrete realities and timelines on the level Harry experiences in such a way that from Harry's and thus our perspective, these interactions happen relatively "simultaneously" and individually. However, I think it is more likely that from the Demonreach perspective, these malleability engines are less discrete and are more of a reality spanning singularity like itself. Sort of.
Which is a really long and arduous way of saying that in my theories there is only one capital "W" DR Warden.
Edit: I'd like to add that I'm really proud of the two analogies of Harry experiences in the NN being like skimming a pond without getting wet (not getting the full depth of the experience, only an aspect of it), and Warden Harry's free will being an "malleability Engine" for the overall Demonreach construct.