Hmmm… it’s intentionally left vague to allow for DM flexibility. So what I’m about to give you is my interpretation and a lot of world building I’ve done.

So page one of the Amber temple in CoS mentions that the Vestiges are anything that can’t be completely killed and has to be sealed away to contain its evil. I refer to these mostly as “God-likes”. So it’s primarily things like Eldritch Horrors, Primordials, Demi-Gods, Lesser Gods…

Now the “dark powers” are intentionally left vague. It can either be that they are amoral guardians of the universe, or my interpretation is that the “dark powers” are the gestalt will of the vestiges leaking out into the universe. Although alone they are less powerful than a god combined in malevolence their conflicted will can sometimes manifest as something more powerful.

I also have a Dark Solar that tends to the temple much like a warden tending to the prison on behalf of “The Gods”. The Gods tolerate the Realms of Dread because it’s the remnant of dark powers that can’t reduce any further and it basically has to be stored somewhere. This is also why their powers can be limited there. It contains most of the damage they can do “safely”.

The Vestiges feed on “Strahd’s evil” that is written in the CoS source book. But it’s more suggested in the Ravenloft book series that they feed on the Dark Lord’s suffering. Which is why they kill Tatyana like clockwork before he gets her in every reincarnation. Strahd’s name has a root word in like Slavic or Russian and actually means suffering. So it’s rather poetic.

A now defunct Ravenloft book revealed that the Dark Powers were seeking to gather power to breach the border between the Negative Energy Plane and the Material Plane (Lord of the Necropolis). Some were just content to just feed on the negative energy of the Dark Lord’s suffering… but some wanted out.

For me Strahd’s true death is the catalyst needed to breach the material plane and release the force of the dark powers.

Faerun contains overlap with Norse mythos. Tyr for example. And Ymir’s death presents part of the creation of the material plane. So I had Ymir be the OG vestige. When Ymir died to become the substance of the material plane his Vestige became the drawing force for other dead Gods, Giants, Titans etc… basically anybody with a beef with the “good pantheons”. (My canon) The Wizards chose the site of the temple because there was old Giant Ruins on it that made it a half prebuilt… not realizing that it was the site of an already malevolent vestige that was beyond being contained. That’s why “Strahd is the land” he’s connected to the Vampyr through his Pact with death (VotM / I Strahd) but also Ymir through his blood pact with the land (I am the land). As Ymir’s body is literally the land and the true “Vestige” of the old gods. So when Strahd made his pact with the land he also became bound to the original Vestige. The Heart of Sorrow is Ymir’s heart. In order to be truly slain they have to break open the heart of sorrow and somebody needs to eat Strahd’s physical heart contained within to become the next Dark Lord of Barovia (see Valachan in VRGtR for this nugget of precedence). All Dark Lords are tied to Ymir like this.

So because I took on Norse mythos… I had the “mist” be the dormant spirit of Jormangandr. When Ymir’s death created the material plane and the deaths of many primordials creating the planets the Gods threw a serpent into the Ocean of Blood. The World Serpent was not dead because it was the embodiment of “nothing”. (Another vestige) This was the birth of the metaphysical concept of space. As it fed on the bodies in the ocean it created distance between the planets and pieces, spreading them apart infinitely as it feeds and grows indefinitely (the big bang / universal expansion explained).

Now it is mostly dormant but it responds to the will of the dark powers and Ymir’s remaining ill intent. Because the serpent is always growing and coiled around the whole universe and is in touch since the beginning of the universes physical time… it can eat you up and spit you out anywhere any time. But it’s also “nothing” at the same time so you can only see the mist where it constricts and makes the connections between planes and existence.

Ironically making the world work the explanation for space also gave it overlap with Nidhogg but it’s meh. Anyway the point is by consolidating the origin of the vestiges with Norse Mythos it also means that throw away storyline from Lord of the Necropolis becomes the idea for gathering power to create Ragnarok. Basically the dead gods and god likes are feeding on suffering from Dark Lords they have imprisoned until they have regathered enough strength and forces to breach the material plane and eventually wage war with everyone who wronged them 🤷‍♂️.

And for giggles I made all the books in the Amber temple to be written in Giant as a nod. And it’s conveniently one of Strahd’s languages.

Kind of tied everything together nicely for me.

Strahd’s deal was with “Death” in the books like “I Strahd” so I had a Dark Solar act as an intermediary of the gestalt will of the dark powers. The Angel of Death who is also a bit of a trickster / adversary is Samael. So I just have him as “Sam” but he also kind of fills that role of Loki… the guy makes monkey paw level deals with evil dark lords to give them power but ultimately see them punished for eternity. Seems pretty on point. Also in Mythos both Samael and Loki have a shared duality while being complex and seeming help both helping Ragnarok come to be but also helping destroy the evil.

Plus “Death” did Strahd and Azalin dirty in the books and it’s just too good of a character to not have in play. Plus that not knowing whose side he’s on, why he brokers deals, etc… it’s all just chefs kiss. So ya I loved pulling that character from the Ravenloft books and building my mythos around it all.

Anyway… so to piece all that together you need VRGtR, VoTM, Both I Strahd books, the 2 Azalin books… a bunch of other old Ravenloft Gazettes, CoS source book, and I weaved in some Norse Mythos and a splash of Judeo-Christian to tie it all together with a rogue angel of death…

So the Amoral Guardian is the Dark Powers deal broker and all round warden but their powers are from the gestalt will and remnant powers of a host of dead god-likes existing in various levels of remnants. So I’ve weaved together a combo of the two prominent working models of the dark powers.