In the 1e AD&D DMG Gary Gygax offers a solution to the existentialist problems of lack of meaning and purpose:
The game is not merely a meaningless dungeon and an urban base around which is plopped the dreaded wilderness. Each of you must design a world (DMG pg 21)
There must be some purpose to it all. There must be some backdrop against which adventures are carried out, and no matter how tenuous the strands, some web which connects the evil and good, the opposing powers, the rival states and various peoples. This need not be evident at first, but as play continues, hints should be given to players, and their characters should become involved in the interaction and struggle between these vaster entities. Thus, characters begin as less than pawns, but as they progress in expertise, each eventually realizes that he or she is a meaningful, if lowly, piece in the cosmic game being conducted. When this occurs, players then have a dual purpose to their play, for not only will their player characters and henchmen gain levels of experience, but their actions have meaning above and beyond that of personal aggrandizement. (DMG pg 112)
According to Gygax, the PCs' existence becomes more meaningful when they are part of a wider world, a world greater than the bare minimum required to play D&D. This greater meaning is realised by becoming a soldier of increasing significance in a cosmic struggle between good and evil, and knowing that one is part of that struggle. Existentialism finds meaning exclusively within individuals, whereas Gygax also finds it in the realm of the gods.
I wanted to riff on this a bit.
I think you're right to draw the contrast with Elric:
What was considered sufficient meaning by Gary Gygax in the AD&D 1e DMG – gaining knowledge of a cosmic struggle and fighting in that conflict as a willing soldier – is considered insufficient by Elric.
To me, the key departure from "existentialist" - but not only existentialist - premises in Gygax's paragraph is the assumption that "vaster entities" and their "interaction and struggle" are a source of meaning. This has been widely doubted since well before Sartre set pen to paper! It goes back at least to Plato's Euthyphro.
What distinguishes existentialism is not just atheism, and not just the rejection of Plato, but the rejection of self-revelatory value. There are (today, at least) many atheist Kantians and atheist Aristotelians, but while they're not Platonists they're mostly not existentialists because they think that value can be identified via reason: eg in the first case, by the exercise of reason, and particular an application of reason to circumstances of metaphysically free beings (ie humans, as conceived of by Kantians); in the second case, by the study of function and purpose as revealed by how things (including humans) work.
Existentialists accept the proposition that humans are free -
radically free - but deny that reason yields value. I personally think Nietzsche gives the best argument for this conclusion, by showing how reason, and understandings of function, are themselves products of historical and cultural development, and hence contingent and so not apt to serve as a basis for self-revealing value. From this philosophical point of view, I think one main purpose of existentialist literature and film is to reveal the contingency of circumstance and duty. This is why we get the recurrent attacks upon conventionality, and upon the ways the conventional represent those conventions, to themselves and to others, as being genuinely valuable.
I think S&S's rejection of conventionality is consistent with those existentialist attacks upon it. I think some of the shock of this is harder to feel today, because of the general post-WWII and even moreso post-1968 abandonment of many "bourgeois" conventions. In Gygax's D&D terms, this sort of self-aggrandising hedonism (as it might seem, for instance, to a typical 19th century moralist) is best represented by CN.
And this is where we see, I think, the clearest rejection of
existentialism by Gygax, in two ways:
This view of the cosmos holds that absolute freedom is necessary. Whether the individual exercising such freedom chooses to do good or evil is of no concern. After all, life itself is law and order, so death is a desirable end. Therefore, life can only be justified as a tool by which order is combatted, and in the end it too will pass into entropy.
First, we have an existentialist outlook contrasted with
good, which Gygax defines in a mixture of Kantian (ie rights, truth) and Aristotelean (ie welfare, beauty) terms. (There is no departure from the Euthyphro here. But there is an affirmation of self-revelatory value.)
Second, and I think even more tellingly,
existentialism is identified with a desire for death. This is a hostile characterisation of the notion of radical freedom, I think. While Conan deals death, the overall tenor of REH's stories is life-affirming, I think. Conan has gigantic melancholy but also gigantic mirth, and loves life.
So overall we seem to have (yet another) case of D&D borrowing tropes but not really the deeper themes or ethos of the literature that inspires it.