Legion is a time-wasting walk through the valley of the shadow of death, where thy plodding plot and thy unintentional laughs are no comfort.

Visual-effects guru Scott Stewart’s debut feature (which he also co-wrote) has a promising premise in line with the classic cheese of Dean R. Koontz or Stephen King. But posh production values and sleek effects are all that separate Legion from King or Koontz TV miniseries on which you’d bail after Part One.

Renegade angel Michael (Paul Bettany) and an assortment of Southwestern saints and sinners (Dennis Quaid, Tyrese Gibson and Charles S. Dutton, to name a few) gather to ward off an advancing apocalypse in a roadhouse that becomes a fortress.

Mankind’s only hope is the unborn child of a chain-smoking waitress (Adrianne Palicki of TV’s Friday Night Lights), both of whom God wants dead. (Some time in the past, some backwoods Bubba’s swimmers spawned the savior of the human race, but why this child, it’s never explained.)

Perhaps “tired of all the bullshit,” God has decided to wipe the slate clean. Because the flood he used last time was so inefficient, this time he employs “angelic” possession of humans to do his bidding.

This apocalypse’s agents are a spindly ice-cream man (Indiana’s own Doug Jones), a foul-mouthed flesh-hungry old lady (Jeanette Miller) and angel Gabriel (Kevin Durand), with the most indecipherable marble-mouth since Boomhauer on King of the Hill.

Legion takes 40 minutes to really get going, and even then, only a chilling motorcade of mayhem (think Field of Screams) gets the blood going.

There’s no enigmatic villain to tempt those tasked to protect the human race, and unlike the far superior The Mist, Stewart never allows these characters to pit their worst fears against each other. He’s too busy cramming in odd homages to Taxi Driver, The Matrix and Terminator 2: Judgment Day, letting John Frizzell’s chugga-chugga score try to pick up slack and mooning over the film’s sound design (admittedly impressive in the Blu-ray’s aggressive DTS-HD Master Audio 5.1 mix).

Looking strangely like Jim Gaffigan, Quaid barrels through with his usual B-movie bitter-beer face and boasts the worst movie haircut since Anton Chigurh. Palicki, exceptional on Friday Night Lights as a woman learning to be strong-willed and independent, is ludicrously asked to basically remain barefoot and pregnant here.

Gibson’s dialogue mainly consists of variations on a theme of, “This shit is crazy, man!,” although he has 2010’s best screamers so far: “I got good at being bad, but being bad ain’t so good anymore” and “Are you asking me to explain the behavior of a motherfucking pestilence?”

And Bettany is far too boisterous an actor for such a glum role as Michael, looking like ’80s-era Sting and acting like Morrissey. That said, Bettany gamely indulges in his own stunts for a climactic battle best described as “wing-fu” — one bit of Legion’s impressive stunt work dissected on the Blu-ray’s special features.

With cast and crew interjections, Stewart hosts Bringing Angels to Earth: Picture-in-Picture, a video commentary atop the film. For those disinterested in revisiting 100 minutes of Legion, there’s great stuff in piecemeal 1080p featurettes.

Stewart’s visual-effects experience served him well, evidenced by Creating the Apocalypse and From Pixels to Picture. (Feel free to skip Humanity’s Last Line of Defense, a self-congratulatory featurette about the ensemble cast.)

Creating is greatly enjoyable, showcasing a shocking amount of practical-effects work employed in the movie over CGI. Prosthetics for the elongated limbs and jaw on Jones’ Ice Cream Man were a cooler idea than anything in the movie itself. The elderly Miller talking about “how I bite a man” is like watching your grandmother talk about a movie she once made with a nice, young fellow. And “previsualization” of the motorcade sequence with Hot Wheels in the dirt is charmingly retro.

It’s too bad that the cast’s description of the Legion shoot as “embarrassingly fun” rarely comes across in the lugubrious final product.