Lost Carcosa itself is the absolute crown jewel set-piece of this story, you owe it to your players and yourself to make it the most bizarre, fucked up, madcap and maddening place this side of Beksinski's and Dali's painting lovechild. Silent Hill, M. C. Escher, a bit of Nightvale, and various surrealist artists were all my inspiration for Carcosa. Envision alien towers, angles that shouldn't be, twisted perspectives, and labyrinthine streets that go nowhere, and you're on the right track. Gravity is wrong, perspective is wrong, and reality's laws have gone out the fucking window. I had them fall up into themselves, I had them go down streets only to have them suddenly dead-end, I had towers leaning over at angles where they should have fallen down. To quote one player, upon seeing hands grasping from a watery basin attached to no apparent body, "This is fucking purgatory." Yes, friend, yes it is. Make it horrendous, and make it disturbing.
On the King, make sure the meeting with him counts. If they don't take his mask off and wake him, have him just... wake up before them, stare them down, and then engage in his mad dance. I had players so stunned and confused at what the King was doing that they had to take a round or two to realize what was going on, and by then the King had nabbed one of them! One player woke the guy up by asking if the "mound of tattered yellow rags" on the throne was Carmichael in disguise. "Carmichael? You there?" He whispered, on tenterhooks. Imagine his terror when the King opened his purulent, glowing yellow eyes and looked at that poor player, who very rapidly realized this was definitely not Anthony he'd just woken up! Then again, it may be worth it to have the King unmask, if only to see those pseudopods, and I quote the Australian version here, "Explode out of his face". God damn, STRAYA, you never stop giving us awesomeness, do you? First the Yith, then Crocodile Dundee and Steve Irwin, and now the wonderful phrase "explodes out of his face". If you don't like the sound of that, friend, I'm not sure you're even human.
As for other characters, the NPCs need some fleshing out at points, but that does help solidify the whole scenario as more an act or a play itself, like it's not quite right. Jessica Barnfeld, Algernon Chambers, and that diva Bianca Vindici are all character gold waiting to happen. Make your players identify with them, then slaughter them mercilessly and they'll never forget it... or forgive you. The more you emphasize themes of fakeness and hidden oddness, decadence, and bizarre surrealism, the more this scenario will work for you. Create atmosphere, build the tension, and watch your players squirm at every little shadow. I personally forced all my players to remain masked from the time they hit the party until the time they entered Carcosa, and the result was glorious. Carmichael himself is best played as ditzy, carefree, and harmless if excitable and a bit camp gay - all the better when his true involvement is discovered, then... As for the house, the less you describe it clearly the better. No map? No problem - the whole thing should feel surreal, dreamy, and strange. Scare your players with odd things that make no sense, and never explain them. Watch them squirm, then profit. Why is there Cassilda here? Where's that noise coming from, and who - or what - is making it? Are those branches scraping at the window, or the claws of some terror? Your players will never know.
Speaking of unknowns, the Stranger in the Pallid Mask has a strong role here - he leads them, beckons them, coerces them, and in the Fatal Experiments copy even tries to kidnap them. It is refreshing to see more aspects of Hastur in play, and fun to use the Stranger as your wildcard. Mine liked to stalk and harangue the players, as if laughing at their slow descent to madness and misfortune... of course, he turned up as the King in Carcosa, though he tragically did not get the chance to explode pseudopods out of his face. And while the NPCs and weirdness may need fleshing out, the props don't. I made up invites, Carmichael's stage notes and mad scrawlings, and many newspaper clips he cut out and scratched on. Any time I get to play a madman is a great day in my book, and this is no exception, I even made the playbill! There's lots of ways to get creative with these props, though only the Fatal Experiments version gives any sort of props - mostly newspaper clippings. Be judicious and have props, but don't overdo it. Keep this scenario flowing and strange, and you'll find it rewarding as all get-out.
Sanity loss is frequent, in small bursts. The idea originally I think was to make Investigators slowly unhinge until they run screaming away from the King, however I feel it could have been implemented just a bit better. Specifically, some of the losses should be upped, and some should be made non-saved, no-roll, "just take it and don't ask why" losses. Some of these include the corpses of the guests. Only 1d3 for seeing someone with all their intestines hanging out? No, absolutely not, unless your Investigators are very used to corpses they shouldn't just be taking 1d3. Some of the deaths are fucking gruesome, I would suggest 1/1d4 SAN loss at least for the more grim ones. And as for seeing and realizing you're in Carcosa, 2/1d10 is not enough, especially for those who read the play beforehand. I'd ramp it to 2/1d12 and make those who read the play immediately take 1d12 of SAN loss, but then again, I'm evil. This is really just a nitpick and not much of a flaw; the campaign's horror and dread is perfectly fine as it is, if you're not evil like I am and don't want Investigators blubbering for their mommies. Seriously, you can't not drive someone mad here; if you haven't at least driven one Investigator to Temporary Insanity or near Indefinite Insanity in this scenario, you are running this wrong.
There's only one real flaw I have with this otherwise perfect gem of an Investigator de-powering exercise (which was how I ran it), and it's sadly kind of major - the ending. The scenario in both versions asks the players to use skills like art/craft and other entertainment/performing skills. This looks neat on paper, but it does seem to cut the horror a bit when your characters are hamming it up while people are dying and tearing their eyes out from viewing The King in Yellow. Yes, it's nice to see little used skills get more attention, but why? Why such a cheesy ending to such a great experiment in terrifying the players? Nobody would ever even think to do this anyway. I wound up changing the ending - my players dropped a chandelier on the sets, distracting the performance long enough to snap people out of the horrible trance the play put them in. Of course, the King was not pleased...
All in all, "Tatterdemalion" is a lot of fun! It's short, it's terrible, and it's sure to give players the shivers. I'm a sucker for surreal horror and the Yellow Mythos, making this a winner for me. The format being all about de-powering cocky Investigators is awesome and it makes for a great change of pace, the fact they go to Carcosa and survive is pretty damn unique, its flexibility is awesome as you can slot it into any campaign easily enough, and its surrealist flavor works well to its advantage. Run this, run this, run this, "Tatterdemalion" is tough to find nowadays but it is well worth the search. It's a serious yellow diamond in the rough, and it succeeds where other scenarios just don't with its meshing together of pure Chambersian surreal terror and Lovecraft's unique blend of existential and emotional dread. Highly satisfying, short, sweet, and terrible in a good way; I give Tatterdemalion a solid 8.5 black stars out of ten. Its only real sin IMHO is that terribad ending it's saddled with, which knocks off a few points. Change that, and you're golden.