Have you seen the yellow sign?

If you do a Google image search for the "Yellow Sign", no doubt you'll get something very similar to this image here.  This one is kinda fancy, with a background and motif surrounding it, but you get the picture.

That sign, however famous, is not the yellow sign, of course.  Robert Chambers, the author who first developed the idea of the yellow sign, never actually described it.  Kevin Ross, who worked on the Call of Cthulhu game for Chaosium, developed that design for a module that was to be published entitled "Tell Me, Have You Seen the Yellow Sign?" as part of the book Great Old Ones.  Curiously, Ross stated in an interview later that Chaosium got the image wrong; it's flipped both vertically and horizontally from how he originally designed it.  Since it was published as such, that's the design that everyone knows, but if it had been published as originally intended, it would instead look like the image on the right.  Maybe it's just due to over-familiarity of the well-known design, but I think the original design somehow has a sense of gravitas that the other lacks.  But, as I said, the actual yellow sign was never described by the author.  In fact, any attempt to graphically represent it by anyone is doomed to fail, since it won't control the mind or drive insane anyone who sees it.  So there's no reason to suggest that either of them has to be the actual yellow sign..

A friend of mine once developed this sign in Photoshop for a banner for me.  It was actually a banner that read DARK•HERITAGE for an earlier version of the setting (and the now long-gone website that supported it) and this sign was placed so as to serve as the • in the setting name.  It's much more traditional looking, being somewhat pentagramish (although not exactly) which I kinda like.  I'm not really very sure how to cause light effects and what not to work in Photoshop, or otherwise I might attempt to do something like this myself (although I don't have Photoshop anymore; so I use a bit of GIMP and mostly Paint.net for my graphics manipulation needs--which are modest, as are my talents.)  For all I know, this could represent the yellow sign.

The yellow sign is, of course, the secret and cursed symbol of the King in Yellow.  The King in Yellow being a creature or entity named Hastur was actually an idea of Derleth's.  Chambers borrowed the name Hastur--he cribbed it from Ambrose Bierce.  In Bierce's original story "Haïta the Shepherd", Hastur was a benevolent shepherd god.  In Chambers' stories, Hastur appears to actually be a place, and the King in Yellow is not Hastur, as near as anyone can tell.  Chambers apparently did nothing other than use the name, not the context or background that Bierce used (he did the same with Carcosa and Hali, which in Chambers/Derleth are also associated with Hastur.)  Lovecraft himself loved the idea of vague references to occult entities and places and stuff, and included a number of items from the brief "Yellow Sign Cycle" of Chambers in some of his stories, mostly just in lists of names of blasphemous places, beings, books, and occult accouterments.  From this, it's not clear what (if anything) Lovecraft intended Hastur to be.  It's listed among a number of both places and beings, and is in fact between two such--with Nyarlathotep and Azathoth (supernatural beings) preceding it, and Yian and Leng (cursed places) following.  Who can say if Lovecraft intended Hastur to be a place or being?  Lovecraft loved to make his references vague, and he did so on purpose. 

"I found myself faced by names and terms that I had heard elsewhere in the most hideous of connections — Yuggoth, Great Cthulhu, Tsathoggua, Yog-Sothoth, R'lyeh, Nyarlathotep, Azathoth, Hastur, Yian, Leng, the Lake of Hali, Bethmoora, the Yellow Sign, L’mur-Kathulos, Bran and the Magnum Innominandum — and was drawn back through nameless aeons and inconceivable dimensions to worlds of elder, outer entity at which the crazed author of the Necronomicon had only guessed in the vaguest way."  -- H. P. Lovecraft, "The Whisperer in Darkness"

Only when Derleth got involved did we get all kinds of controversial detail on Hastur, who was now combined with the figure The King in Yellow, and given all kinds of familial affiliations, a more detailed physical description, and more.  He apparently was also combined with the figure listed above, Magnum Innominandum, which is loosely translated from Latin as He Who Must Not Be Named.  (It's loose.  A more literal translation would be Great Unnameable.)  Because The Call of Cthulhu game almost without exception followed Derleth's lead (and in fact went even much further down the exact same path of quantifying and detailing in systematic ways) many fans of the Mythos, which was arguably kept alive and in front of the public eye because of Chaosium (either that because of the Cthulhu Mythos chapter in the first printing of D&D's Dieties & Demigods which followed the same pattern anyway of a very Derlethian interpretation,) accept that definition without comment or complaint.  Ironically, many of these same folks are those who, if asked, may be disparaging of Derleth's influence on the Mythos.

Art by Mads Herman Johansen

In DARK•HERITAGE, the King in Yellow is not Hastur.  There is no Hastur (that I know of yet, anyway) in DARK•HERITAGE.  The King in Yellow is a title given to the being known popularly in the Terrasan language as Caronte, from ancient Terrasan Charun or Charon.  His features are always obscured; he usually appears as a very tall, gaunt vaguely humanoid figure wrapped in tattered yellow rags.  His face is always obscured, either by the yellow hood, or sometimes by a pallid mask.  Ancient, whispered tales tell that to glimpse Caronte's true face is to go insane or drop stone dead instantly.

He's sometimes depicted riding a pale, or even sickly or skeletal horse, and carrying a staff or scythe with the yellow sign inscribed on the handle.  He is commonly associated with Death.

Finding "truth" about the supernatural in DARK•HERITAGE is often problematic.  Ancient tomes and scholarly books mention many things that are otherwise forgotten, but such books are often banned and suppressed due to their dangerous and sinister nature.  Even if the aspiring occultist can find them, he'll find that such tomes are riddled with inconsistencies and contradictions, not only from one book to another, but sadly often within the same book.  The authors of many of them were under severe mental strain in many cases, and outright insane in others.  While such fevered insane visions as they had are often the source of their knowledge, it did not make any reality behind it easy to interpret, and it begs the question of how much they knew what they were writing about anyway.  Although Caronte is a commonly called upon by Terrasans and others, and is recognized as a "god" of the setting, with the power and ability to affect the lives of those who live therein--details about him are sketchy, and many skeptics can point to numerous non-divine sources for many of the stories and details that are associated with Caronte (and others) in the pantheon, calling into serious question its veracity.  Many proponents of this "non-divine" interpretation of the Mythos believe that the King in Yellow--and indeed many of the gods worshipped by the Terrasans and others, are actually powerful, pre-human and alien supernatural beings who slumber fitfully in the Forbidden lands, locked away in their mountain fastness in Kadath, or in the King in Yellow's case, perhaps occasionally wandering the deserted and wind-swept streets of ruined Carcosa on the edge of the Plateau of Leng and Lake Hali. 

Vague and tantalizing hints suggest that the ancient play "The King in Yellow" is, however, a real document, that was once performed in Old Terrasa before the Empire started to decline.  When performed, the nobility and parvenus in the audience rioted, and many were killed or confined to asylums permanently, thinning the ranks of the gentry for generations.  The yellow sign is also real, according to these vague hints, and some few have claimed to have seen it and lived at least long enough to report having done so, although most frequently not much longer than that.  Some vague hints even claim that Camilla and Cassilda--mortal companions of the King in Yellow mentioned in the play of the same name, are based on real people who survive either as spectres or immortal, cursed souls of some kind, wandering the Mezzovian region looking for release from an eternity that's gone mad.