What would horror screenwriters do without murderously sadistic millionaires? They’re so very handy when you’re trying to concoct a means for putting say, eight reality TV and streaming show stars in a “Funhouse” where online viewers can revel in them slaughtering each other.

Actor turned writer-director Jason Lee Williams (“The Evil in Us”) tries on that tired trope as the “brains” and bucks behind “Furcas’ Funhouse” in his foot-dragging variation on the “And then there were none” theme.

It’s a not-quite-soulless slaughterhouse thriller with dull deaths, drab staging and funereal pacing. So even the visceral promise of its premise fails to pay off.

Valter Skarsgård, Khamisa Wilsher, Gigi Saul Guerrero, Christopher Gerard, Karolina Benefield, Amanda Howells, Mathias Retamal and Dayleigh Nelson portray assorted “personalities” recruited for this show that almost celebrates the golden age of “fame whores.”

One’s an MMA fighter on the ropes, another is a ruthless celeb gossip blogger, one’s an Instagram bombshell, another’s a reality bachelorette, and so on.

They all wake up, drugged, in a remote, sealed-off mansion filled with cameras where they will fraternize, “confess” their true feelings to viewers in a booth and “compete” for a $5 million prize. They all had agents who arranged this, so they have no idea what “only one of you will be with us to collect the $5 million prize.”

Still, “It was in your contract.”

Our oligarch (Aussie Jerome Velinsky of “The Evil in Us”) loves Beethoven and appears to his contestants as a CGI talking panda, serving up exposition, endless “rules” and “competitions” (“Pinata Party” involves beating somebody to death while blindfolded and not realizing you’re doing it), insults about each of the eight’s backstory and popularity polls results from online viewers telling us who gets to fight to the death, or face torture and and execution.

There’s TV “coverage” that looks little like real cable TV, a flippant, “This must be fake” youtube “reviewer (Bradley Duffy) snarking away about the show, shots of slack-jawed viewers of all ages gulping down this latest serving of “the Kardashianization of humanity,” and an ever-shrinking populace of “Funhouse” contestants, who don’t resist this dehumanizing murder-for-entertainment, unless you count whining about it as “resistance.”

“We had a DEAL!”

And there’s the “outside” search, by police, for where this mass murder is being staged, as drably-handled as everything else.

The surprises don’t amount to anything that improves our appreciation of what’s happening, although a couple of the players — Gerard’s MMA fighter “Tombstone,” and Wilsher’s utterly out-of-her-depth “Bride to Be” star in a kill-or-be-killed “game” — stand out.

There’s an audience for this sort of crap — bloody hackings, dismemberments, sex and (female) nudity. But even fans will be put off by the moronic “sermons” by the pontificating rich guy/panda and the “Moonlight Sonata” pace of a no-fun-allowed “Funhouse.”

MPA Rating: unrated, graphic violence, nudity, profanity

Cast: Valter Skarsgård, Khamisa Wilsher, Gigi Saul Guerrero, Christopher Gerard, Karolina Benefield, Amanda Howells, Mathias Retamal, Dayleigh Nelson, Bradley Duffy and Jerome Velinsky

Credits: Scripted and directed by Jason William Lee. A Magnolia/Magnet release.

Running time: 1:46