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For the third installment in one of the most unexpectedly enduring antihero sagas in recent memory – and what was, by all accounts, a labor of love for its star and writer-director – Riddick is a bizarrely unambitious film.

The first movie, Pitch Black, was a high concept creature feature about a bunch of spacefarers stranded on a planet that’s perpetually in sunlight; until an eclipse plunges all into darkness and hordes of predatory winged echolocating beasties emerge from underground. It more or less launched Vin Diesel’s career by casting him as the titular convict and all-around badass.

The next film, Chronicles of Riddick, leapt fully into the realm of sci-fi fantasy, squaring Riddick off against a crew of bounty hunters, some armored cougar-like creatures, and an entire army of world-destroying religious fanatics. It also, unfortunately, consigned itself to a PG-13 rating.

Chronicles didn’t do so well in theaters, so Diesel finagled his way into rescuing the rights to the franchise from Universal. Then he and David Twohy, who wrote and directed all three films, put the production for Riddick together themselves. Diesel even leveraged his house, making Riddick something of a high-powered indie auteur effort, with some considerable sci-fi genre pedigree. You’d expect good things.

And for the first act, at least, you get them. The film opens on an unnamed planet, with Riddick stranded and left for dead by the Necromongers – the aforementioned army of religious fanatics. Convinced he’s lost his edge, Riddick decides to hack out a solitary existence amidst the planet’s volcanic wastelands, getting back to his core nature of badass-ness. He deals with hunger, a broken leg, poison pools, and the perils of taking in a local dingo-like predator as a pet. Finally, there’s a canyon passage to greener lands, guarded by what I can only describe as a slimy alien scorpion monster.

The practical challenges of survival – and of outwitting said scorpion monster – create a cool little mini-story of self-actualization that concludes all too quickly. Once through the canyon, Riddick discovers an abandoned outpost and winds up bringing not one, but two teams of bounty hunters down on his head. Then a rain storm rolls in, and the water awakens a whole swarm of the scorpion monster’s cousins, apparently hibernating under the dirt of the plains. Or something.

And that’s really the whole movie. Both the bounty hunters and Riddick’s newfound alien canine companion ape aspects of the previous films, but generally in ways that are an improvement. Not so the scorpion monsters, which are lesser echoes of the elemental beasts from Pitch Black, right down to the odd two-legged lope. To Riddick’s detriment, the monsters provide most of the narrative drive for the second half, making it apparent for the last hour that the movie isn’t going to break any fundamentally new creative ground. The opening even hints at the possibility that Riddick will finally see his home world, only to utterly abandon the notion until the denouement, as an obvious tease for a fourth movie.

In keeping with the previous films, Twohy tries to give Riddick something of a moral reckoning at the climax. It sort of works, but the “been there, done that” cloud hangs heavier over the proceedings than those monster-awakening thunderheads.

But to his credit, Twohy’s direction has never been more confident and immediate: this is hands down the best looking of the Riddick films. The character work is also strong.

Both teams of bounty hunters – one a crew of highly professional mercenaries, the other a ragtag bunch of dry-witted ruffians – all stand out as individuals. There’s Jordi Mollà as Santana, the oily and repellent leader of the ruffians, whose delightfully gory end more than satisfies the R-rating; Katee Sackhoff as Dahl, the professionals’ steely-jawed and fiercely loyal female warrior; and Matt Nable as Johns, the professionals’ leader, who brings an appealing mix of competence and controlled emotional vulnerability to a character with a personal connection to Riddick’s past. (It’s also an improbable connection, given the actor’s relative youth, but we’ll assume anti-aging therapy is well advanced in the future.) Johns is the one who ultimately tries to speak to Riddick as a human being, and it’s one of the film’s most arresting moments.

It’s not so much that Riddick is bad, per se. I can understand budget constraints, and Twohy’s stripped-down, character-centric approach to the narrative actually works pretty well. He even pulls the neat trick of shifting perspective from Riddick to the bounty hounders halfway through, reinforcing Riddick’s mystique as a force of nature.

What I can’t understand is taking the one genuinely new thing the film does with the character, and tossing it aside after thirty minutes in favor of warmed-over plot reruns from earlier outings.