Hastur. Our final Great Old One from the Bestiary 4. Assuming, that is, that he actually is a Great Old One, since there’s evidence that his King in Yellow manifestation is actually just an avatar of a greater Hastur who is an Outer God. So the short version is that he’s seriously bad news.
I won't even get into Hastur’s origins, since we have Wikipedia for that. Suffice it to say that Hastur/the King in Yellow goes all the way back to Ambrose Bierce and especially Robert W. Chambers in the 1890s. Practically a meme from the beginning—think Slender Man for the literary set—he’s found his way into works from Lovecraft and Derleth to Stephen King to The Forgotten Temple of Tharizdun and Dungeon magazine (Matthew Hope’s “And Madness Followed”). And where he goes, the Yellow Sign follows—and with it, madness.
Hastur is by far the most flexible and utilitarian (in a good way) of the published Great Old Ones. Bokrug is fine as a final boss monster in terms of statistics, but you’ll have to do a lot of work to build him up, as he’s not exactly a marquee name. (He’s not even evil!) Cthulhu is a problem on the opposite end of the scale—once you open that box, it’s open. With all his baggage, once your players know they’re facing Cthulhu you’re playing a different kind of Pathfinder. (One might even argue you’re playing…oh, I dunno, Call of Cthulhu.) And once you’ve invoked Cthulhu you pretty much have to end with a really nasty Big Bad—a supremely powerful cultist or one of his CR 20 star-spawn, if not the Dreamer in the Deep himself.
But Hastur… Well, the Yellow Sign has cropped up throughout the multiverse. PCs might face Hastur’s minions once and never again. Or, drawn to the chaos surrounding them, the King in Yellow himself might interpose in their final adventure, as one great penultimate hurdle, one last complicated surprise to be tamped down before the party can face their final foe.
Yet at the same time, if you want a Great Old One to be in you game from Day One, there’s no better place to start than with Hastur. In their first adventure, PCs find strange yellow glyphs in the bad guy’s lair. As they progress in levels, they occasionally spot golden graffiti whose meaning eludes them. The Sign pops up again at the asylum they clean out, then at the opera, then at the club for decadent nobles. And soon they’re battling serious monsters, serious cultists, serious creatures from other worlds/stars/times/realities…and then finally the King in Yellow himself. And gods forgive them if they touch his tattered robes…
Adventurers find themselves compelled to collect the pieces of an opera—a work of music, text, dance, and stagecraft that seems to promise great rewards. Only as the publication date of the collected work nears does the dark nature of the manuscript begin to reveal itself. Now the adventurers race against time—not to mention the aeons and inevitables who accuse the party of having threatened reality, and the proteans who want to devour the world—to stop the work from being published. If the opera is performed, Hastur will enter this world—and the more complete the preparations have been, the greater his power will be.
Plane-hopping adventurers flee the Plateau of Leng and its monstrous denizens only to arrive at the shores of the Lake of Hali on Carcosa. Populated by chaotic divs and azi, the cities of this place seem to crumble as the adventurers watch, then spring to life behind them. Eventually, they meet the only true humanoids in this place—the Wizards in Marigold—who welcome them (and then trap them) in their sprawling complex, assuring them that the Master will be coming soon and that he longs to meet them face-to-face.
In the early Middle Ages, Charlemagne and his knights save the Pope from being torn apart by Romans driven mad by the Yellow Sign. In the 1600s, Cardinal Richelieu’s rule is autocratic and sometimes cruel for a reason: Only he knows the House of Bourbon has given itself over to Hastur. (Indeed, even the gold fleur-de-lis of France’s heraldry is a sanitized nod to Hastur’s influence.) And on the barricades of New Eiffel in 2400, young technomancers and cyberberserks battle the morlock thralls and robot servitors of the Carcosan invaders. Roughly every 800 years, Hastur threatens to destroy France…and now adventurers from three eras in history will unite to take the fight to Hastur’s mad home.
—Pathfinder Bestiary 4 140–141
Tharizdun is not quite Hastur (for one thing, he’s more elemental-y or Far Realm-y or Abyss-y, depending on the edition), but he’s also not not Hastur. In other words, it’s up to you.
Hastur is also the only Medium published Great Old One, meaning he’s a terrifying threat that doesn't have to level buildings to destroy the world.
Back when I did my big countdown of the D&D 3.0/3.5 books I thought every Pathfinder GM should have, I put the Book of Vile Darkness at #1. I go back and forth over whether that was the right call, but if you’ve got Hastur in your game, it’s a must. From feats like Dark Speech to rules for sadism and masochism to some really nasty Vile spells, there is no better was to portray a cult of decadent nobles and actors who are inexorably giving themselves over to evil.
Once again, apologies for the incompleteness (for Tumblr readers) or flat-out absence (for Blogger readers) of yesterday’s post. I had a work function that kept me out till nearly midnight, then I got home only to find my laptop had no juice and I’d left my charger at work. The full entry is now up on both sites.
(I probably can’t get away with too much sad violin music, because the work function was going to see the touring production of Chicago and then being lucky enough to go to the cast party afterwards. My life is hard sometimes. For you theater/TV geeks out there, I did not meet John O’Hurley (Seinfeld’s J. Peterman), but he was great in the show.)