Monsters have made for some of the greatest movie antagonists, with the best of them having been able to terrify and enthral in equal measure. From Dementors to dinosaurs, there really is something for everyone – and although these creatures may look horrifyingly realistic, over the last four decades many of these have actually been the result of computers going bleep for months on end.

CGI has come a long way in the years since the technology first emerged, and today it can be hard to distinguish between special effects and reality. There have been some CGI misfires over the years, for sure, but there’s nothing quite like a CGI movie monster done right – and here we’ve picked out our 20 favourites.

20. Unnamed monsters (A Quiet Place)

John Krasinki’s directorial debut, A Quiet Place, surpassed box office expectations in 2018 and quickly solidified itself as a favourite of the horror genre. The film sees a family struggle to survive in a world filled with monsters which, though blind, have unusually acute hearing. As scary as these beasts are in concept alone, they’re even creepier to look at.

As reported in Vanity Fair in 2018, “the team immediately set about pulling references; prehistoric fish, black snakes, and bats, particularly their movement patterns. Inspiration was also drawn from bog people: cadavers that have been mummified in peat, turning the skin black and giving it a sagging, leathery look.”

19. Dementors (Harry Potter series)

The wizarding world of Harry Potter is filled with all many of wonders, both enchanting and terrifying. Of all the franchise’s spectacular creations, none are quite so intimidating as the Dementors, the black-cloaked wraiths that guard Azkaban prison and suck out the joy of all who cross their path.

For their first appearance in Harry Potter and the Prisoner of Azkaban, director Alfonso Cuarón was originally keen to move away from CGI effects in favour of puppetry. However, this proved too costly and CGI was used instead, although footage of Dementor puppets moving underwater was used to inform the eerie, floating feel of the creatures.

18. Davy Jones (Pirates of the Caribbean series)

You know when you have far too much calamari at the buffet? Well, that’s what Pirates of the Caribbean villain Davy Jones feels like every day, since he’s literally part squid and part man. The aquatic antagonist is portrayed by actor Bill Nighy, but the character’s facial effects are the result of some rather advanced digital effects.

Remarkably, the character was created almost completely from CGI: Nighy wore a prosthetic only once, for the scene in which Orlando Bloom’s Will Turner steals a key from within his tentacle beard. The extent and success of this CGI surprised even the filmmakers themselves, who had filmed extra shots using more traditional make-up which they ultimately didn’t need.

17. The dinosaurs (Jurassic Park)

1993’s classic monster movie Jurassic Park was produced in a time when CGI was still in its infancy, yet the film’s digital effects are extraordinarily realistic and still up even today. This is in part because of how the film merges CGI with old-fashioned practical effects and animatronics, so seamlessly that it’s often hard to tell the difference.

In post-production, the effects team used so-called Dinosaur Input Devices, which allowed for the CGI dinosaurs to be manipulated like stop-motion puppets, which was a painstaking process. For every frame of the T-Rex in the rain, the effects took six hours to render – and, if you recall, there’s a lot of rain in this movie.

16. Gollum (The Lord of the Rings: The Two Towers)

Is Gollum a monster or a man? That’s the driving conflict of the character in The Lord of the Rings trilogy, but any way we look at it the character as presented in Peter Jackson’s movies is a technical marvel. Gollum’s arrival in The Two Towers marked a watershed moment for the blending of CGI and live-action footage, as while he may be animated, he is performed by actor Andy Serkis.

FX company Weta Digital had begun animating Gollum as early as 1998 (four years prior to the film’s release). Interestingly, every scene with Gollum was filmed twice: once with Serkis physically present, and once without. They soon discovered that having Serkis in the scene drew a much better performance from his co-stars, so the ‘without’ scenes were scrapped.

15. Clover (Cloverfield)

The first trailers for 2008’s Cloverfield were released without a title, producer JJ Abrams and co. hoping to build intrigue with the found footage shooting style and tiny glimpses of a massive monster. This approach worked: audiences showed up eager to see the mysterious beast attack New York, and its ultimate reveal was not a let-down.

While never given in a name in the film (government officials refer to it only as a Large Scale Aggressor, or LSA), the monster was affectionately nicknamed Clover by production staff. 25 storeys tall and brimming with teeth and bug eyes, you might be surprised to learn that Clover is intended as an infant of its species, with larger versions glimpsed in 2018 sequel The Cloverfield Paradox.

14. The Homunculi (Don’t Be Afraid of the Dark)

Don’t get suckered by the title: Don’t Be Afraid of the Dark gives viewers plenty of reasons to be nervous when the lights go out. Starring Katie Holmes and Guy Pearce, the 2011 film is a remake of the 1973 made-for-TV film of the same name, with a larger budget and the esteemed Guillermo del Toro on producer duties.

The film didn’t prove a big hit, but its CGI beasties the Homunculi deserve appreciation. Inspired by mole rats, the creatures are almost completely blind and hairy in all the wrong places. These monsters, the film tells us, drag human beings into their ashy pit and make them into monsters themselves. Yikes.

13. Kong (King King (2005)

King Kong has graced the screen many times in many forms. The stop-motion animation of the 1933 original is still impressive; the man-in-suit approach of the 1976 remake, less so. When Peter Jackson took on the story in his 2005 version, many complained it was overlong and overblown, but few could fault the special effects.

Jackson’s King Kong presented us with the first entirely digital take on the mighty ape, once again portrayed by Lord of the Rings actor Andy Serkis via motion capture technology. The result is a vibrant, frightening but also sympathetic monster which truly feels alive at times – and that’s not to mention how amazing the film’s CGI dinosaurs are as well.

12. Arachnids (Starship Troopers)

Hailed by some as a satirical masterpiece and dismissed by others as a braindead blockbuster, 1997’s Starship Troopers is one of the most divisive sci-fi films ever made. Despite this, the film was nominated for Best Visual Effects at the Oscars, as it boasts some of the most remarkable CGI monsters of the era.

Variously known as Arachnids or simply Bugs, the antagonists of Starship Troopers are giant, inarticulate insects from a distant planet who are at war with the human race, resulting in large scale carnage. The bulk of these are comparatively small soldier bugs with sharp limbs, but there are also a few considerably larger ‘tank’ bugs which look like giant militarised cockroaches.

11. The bear (Annihilation)

2018’s Annihilation was one of the most abstract and genuinely nightmarish science fiction films in recent memory, anchored by strong performances from a largely female cast led by Natalie Portman. However, we can’t fail to mention that the film also boasts a wonderfully monstrous CGI creation.

The terrifying, mutated bear-like creature is only seen in brief glimpses, which serves to make it all the scarier. After it captures Tuva Novotny’s Cass and drags her away into the forest, the idea is that its own DNA merges with that of its victim, which the film’s FX artists brought to life by literally merging a scan of a bear skull with that of a human skull.

10. Edgar the Bug (Men in Black)

1997 sci-fi comedy adventure Men in Black has no shortage of entertaining extra-terrestrial creations merging CGI and practical make-up effects. However, the most impressive of the lot has to be the film’s main villain, Edgar the Bug, played in his initial human form by Vincent D’Onofrio, but bursting forth to reveal a mighty bug in the final scenes.

According to the Men in Black Blu-ray commentary, physical effects were prioritised for static characters and CGI was used for more mobile aliens. Since he towards the end of the film crawls up the side of a building and starts trying to crush the protagonists, Edgar fits in the latter category. When the final showdown with Edgar was changed from an existential debate to an action sequence, it cost filmmakers an extra $4.5 million.

9. The Behemoth (The Mist)

Based on a Stephen King novella, The Mist sees a community of ordinary people stranded in a supermarket when their home town is swept up in a mysterious mist filled with monsters. While the story deals with the horrors of which human beings are capable under the most dire circumstances, this doesn’t detract from how truly horrible the film’s CGI creatures are.

While The Mist’s multitude of pterodactyl and praying mantis-like creatures are scary in their own right, surely the most alarming of the lot is the one known as the Behemoth. As the nickname might suggest, it’s an absolutely gargantuan terror, boasting six legs and tentacles for a face. While not it may not be overtly hostile, the creature gives us some indication of how ants might feel when we walk blindly past.

8. Dormammu (Doctor Strange)

In common with most Marvel Studios productions, 2016’s Doctor Strange provides a feast for the eyes with top-of-the-line CGI in abundance as Benedict Cumberbatch’s former surgeon learns the mystic arts. So it makes sense that the film’s ultimate villain, Dormammu, gets the same treatment.

Described as “a primordial inter-dimensional entity who wields apocalyptic levels of supernatural power,” Dormammu is a gargantuan, almost god-like cosmic being (portrayed by Stephen Strange actor Benedict Cumberbatch himself via motion capture technology). Some fans might have complained this wasn’t accurate to the comics, but most just enjoyed the spectacle.

7. Prawns (District 9)

Director Neill Blomkamp’s use of CGI has always been on-point, as proved by the FX artist-turned-director’s first feature film, District 9. On a budget of just $30 million, this 2009 sci-fi drama presented some of the most astonishingly realistic CGI aliens ever seen on film.

You might assume that the so-called ‘prawns’ are human actors augmented with CGI, but these alien characters are actually 100% digital. Blomkamp intended for the creatures to initially be disgusting, but for them to eventually show enough emotion that audiences would empathise with them.

6. Non-Terrestrial Intelligence (The Abyss)

Writer-director James Cameron has always been at the front lines of the CGI boom. The technology broke through in a big way thanks to Cameron’s 1989 movie The Abyss, which presented the most impressive digital creation ever put on film up to that point.

Set almost entirely underwater, The Abyss features aliens unlike any other, most memorably showcased in the form of a sentient tentacle of water which imitates the face of actress Mary Elizabeth Mastrantonio. This still jaw-dropping CGI creation earned FX company Industrial Light & Magic a Best Special Effects Oscar.

5. General Grievous (Star Wars Episode III: Revenge of the Sith)

The Star Wars prequel trilogy is frequently derided as the moment that Hollywood’s use of CGI hit saturation point, thanks to the overabundance of both digital backdrops and digital characters, many of which proved cartoonish and unlikeable (yes, Jar-Jar, we’re talking about you).

Thanks goodness, then, for Revenge of the Sith’s General Grevious, an alien cyborg warlord who collects the lightsabers of his defeated enemies. From his vivid yellow eyes to the sparse remnants of flesh seen beneath his armour, Grievous is terrifying and barely recognisable as a humanoid creature, particularly when his arms split and he crawls around like a spider.

4. Shelob (The Lord of the Rings: The Return of the King)

Movies love spiders. Whether it’s the real things, as in Arachnophobia, or the more often employed CGI variety, there’s nothing more terrifying than an eight-legged beast made of eyes and teeth – except for enormous eight-legged beasts made of eyes and teeth, which is exactly what Peter Jackson delivers in The Return of the King.

Shelob features earlier in Tolkien’s books, but her portrayal in the third instalment of the Lord of the Rings movie trilogy is worth the wait. While a less generous viewer might suggest the night-time fight against Shelob helpfully conceals the CGI arachnid, there’s no doubt that the darkness heightens the tension. For anyone who doesn’t like spiders, it’s easily the scariest sequence in the epic trilogy.

3. The Jötunn (The Ritual)

Continuing our recent fascination with all things Scandinavian, 2017 horror The Ritual sees a group of stranded campers attacked by a Jötunn, a giant-like creature and spawn of Loki. As with many horror films, the creature remains hidden until later in the movie – but when we finally do see it, it’s suitably terrifying.

Part stag, part man, and part something else we don’t really want to consider for any significant period of time, the Jötunn impales people and demands human sacrifices. The construction of the CGI monster is particularly impressive considering the wooded setting, which forces the creature to traverse between trees and through leaves, and all sorts of terrain that makes for animators’ nightmares.

2. Trespasser (Pacific Rim)

2013’s Pacific Rim is one of director Guillermo del Toro’s biggest hits, with a simple but irresistible premise: giant robots duking it out with giant aliens. Historically such spectacles were brought to life with men in suits (famously in the Godzilla movies, and TV’s Power Rangers), but Pacific Rim utilises cutting edge CGI.

We could pick any number of the Kaiju (or ‘strange beasts’) for this list, but we’re going to focus on Trespasser. The first beast to attack San Francisco, it’s terrifying and awe-inspiring in equal measure, with its hardened shell, gargantuan claws and mighty cranial ridge (which also earned it the nickname ‘Axehead’). With this mean monster showing up first, we know to expect trouble as the film goes on.

1. The Mummy (The Mummy (1999)

The Mummy franchise has had its fair share of CGI disasters – but before Dwayne Johnson ever got involved, the series was known as something of a visual effects pioneer. The 1999 reboot of the classic horror series made the ancient Egyptian antagonist Imhotep made flesh, eventually fully transforming into the svelte Arnold Vosloo (and not Billy Zane, as many fans seem to think).

Starting out as little more than a skeleton, over the course of the movie Ihmotep gradually becomes more human, but so too do his over-worldly powers over the elements increase, conjuring tidal waves and sandstorms with his face. These effects were pretty groundbreaking for 1999, but they came at a price – $15 million of the production’s $80 million budget, to be exact.