While horror movies have remained consistently popular over the decades, the popularity of various sub-genres varies hugely. From possession movies in the '70s to the slasher film of the '80s, all it takes is one big horror hit to inspire dozens of homages, copycats, and rip-offs.

Despite the huge advances in digital effects that had occurred throughout the '90s, the 2000s were marked by the rise of the low budget found footage movies which followed in the wake of Blair Witch Project in 1999. The result was a noticeable dip in the number of great monster movies, in comparison to the previous decade. With audiences seemingly happy to sit and watch a bunch of non-actors being scared by an unseen supernatural threat on a shaky camcorder, why bother with the hassle of creating terrifying and imaginative monsters?

But of course, there's never been a decade without a few great monsters. While CGI was still emerging in the '90s, by the 2000s it meant that filmmakers could fully embrace it as a tool to create convincing cinematic creatures, with some hugely entertaining films delivered by big names such as JJ Abrams and Bong Joon Ho. Equally, there were still some directors who kept the tradition of physical make-up effects alive too--most notably Guillermo Del Toro, who continued the tradition he started in the '90s and created some of the decade's most iconic screen creatures. So with Halloween now upon us, here's some of the scariest movie monsters of the 2000s....

10. Bioraptors (Pitch Black, 2000)

This clever and scary sci-fi chiller gave Vin Diesel one of his best roles--the notorious convict Richard B. Riddick--and introduced some really cool monsters as well. The Bioraptors live on the planet M6-117 and due to their extreme light-sensitivity, only appear on the surface once every 22 years, when a huge eclipse plunges the planet into darkness. Pitch Black features some terrifying scenes as the taloned creatures attack in a massive swarm--after 22 years, they are damn hungry.

9. Craig (Creep, 2004)

Not to be confused with the recent comedy horror movies of the same name, this Creep is the directorial debut of Christopher Smith, who also made movies such as Triangle and Severance. It uses the tunnels of London's subway network as a highly effective setting, where a woman is trapped overnight and becomes the target of a terrifying humanoid creature named Craig. Craig was abandoned underground as a young boy and has grown into a deformed, deranged cannibal who keeps his victims in cages as they await their gruesome death. Chillingly played by Sean Harris, who is best known for his villainous role in the last two Mission Impossible movies, Creep proves that terrifying monsters don't always need outlandish vfx to be scary.

8. The Angel of Death (Hellboy II: The Golden Army, 2008)

Guillermo del Toro is unquestionably the modern master of monsters. The Hellboy movies feature some of his most inventively weird creations, and there are few more memorable that the Angel of Death in Hellboy II. Played by del Toro's regular creature performer Doug Jones, this demonic, grinning figure holds Hellboy's fate in her hands in a key scene towards the end of the movie. Like Pan's Labyrinth's Pale Man, the Angel's eyes are located elsewhere on her body--in this case on her wings--with the top-half of her head replaced by a weird cracked organic disc. Or something.

7. Crawlers (The Descent, 2005)

Neil Marshall's claustrophobic chiller is one of the most effective horror films of the decade. It focuses on an all-female team of cave explorers, who become trapped deep underground with something very scary down there with them. The Crawlers are blind sub-human monsters who seek out their prey by letting out terrifying shrieks and using the bouncing sound waves to work out where they are--much like bats and dolphins. Marshall uses the dark caves and these otherworldly sounds to produce something truly scary.

6. Grant Grant (Slither, 2006)

Guardians of the Galaxy and The Suicide Squad director James Gunn might now be one of the biggest names in superhero movies, but his filmmaking roots lie in horror. His 2006 movie Slither was a gory and hilarious body horror comedy with a great cast (Elizabeth Banks Michael Rooker, and Nathan Filion) and an even better monster. An alien parasite crashes near a small town and takes over the body of a wealthy local man (Rooker), transforming him into a weird, slimy, tentacled monster able to split a man in half with one quick strike from his gooey tendrils.

5. Ginger (Ginger Snaps, 2000)

When it comes to movie monsters, there haven't been nearly as many werewolf movies as vampires or zombies over the years--possibly because convincing werewolf transformations aren't as easy as popping some fangs in or slapping on some undead facepaint. But there have been some classics, and one of the best is Ginger Snaps, a teen horror movie, in which a pair of young sisters deal with the fact that one--16-year-old Ginger--has developed lycanthropy alongside the usual changes that teenage girls go through. Like Amerian Werewolf in London and Cronenberg's The Fly, the great strength of this movie is the huge sympathy built for its characters, so that when Ginger does indeed "snap," the monster is far more than just a bloodthirsty beast.

4. Mist Monsters (The Mist, 2008)

Sometimes the scariest monsters lie in our imaginations. Frank Darabont's brilliant adaptation of the Stephen King novel covers an entire town in thick mist, in which terrifying creatures lurk. We see some of them in detail--flying scorpions and scuttering spider-like beasties--but the biggest and scariest are half-glimpsed in the fog, like the giant Behemoth and the deadly "Arachni-Lobster." Knowing that an otherworldly creature could appear from the mist at any point makes for a highly effective and unsettling experience.

3. Clover (Cloverfield, 2008)

While the found footage craze of the last decade mostly produced low-budget horror movies, there were a handful of large-scale examples that worked well. Cloverfield was the directing debut of upcoming Batman helmer Matt Reeves, and was produced by JJ Abrams. It combined the best of both worlds. The found footage technique meant that the movie was scary and immersive, while the bigger budget allowed for some fantastic visual effects, as a giant Godzilla-esque monster (termed Clover during the movie's production) lays waste to New York. What makes Clover so scary is the way it is seen from street level as our heroes attempt to escape from the city, rather than the aerial shots we are used to seeing in this type of movie.

2. Gwoemul (The Host, 2006)

South Korean filmmaker Bong Joon Ho is currently receiving much acclaim for his stunning drama Parasite, but 13 years ago, he also delivered one of the 2000's best monster movies. The Host focuses on a huge, amphibious creature that emerges from Souel's Han River to terrorize the city. The monster is the mutated result of hundreds of formaldehyde bottles being dumped in the water several years earlier, and it also carries a deadly virus that can infect anyone who gets close. Bong stages the thrilling monster attack scenes with his usual skill, and in a genre with so many giant hungry reptiles, it's nice for the amphibians to get some representation.

1. Pale Man (Pan's Labyrinth, 2006)

Perhaps the most iconic and terrifying monster in Guillermo Del Toro's filmography, the Pale Man is the child-eating humanoid creature that Ofelia must face in Pan's Labyrinth. Played by Doug Jones, the moment in which this creature places his eyeball-hands on his face remains a classic, unforgettably chilling moment. It's a testament to the Pale Man's terrifying ubiquity. Even though he has only a few minutes of screentime, he has become one of the defining images for the movie, and the first thing that many fans think of all these years later.