50 Best Sci-Fi Horror Movies of All Time (RANKED)
Sci-fi and horror may appear to be mutually exclusive. Making an effective horror film needs talent. Creating a decent science fiction horror film needs a certain amount of creativity. This hybrid genre is possibly the ultimate exercise in suspension of disbelief, whether it’s brilliantly illustrating the science underlying the tale or creating an environment that keeps the spectator interested and glued to the screen.
The last couple of decades have been fantastic for fans of science fiction and horror, two genres that complement one another perfectly given humanity’s ongoing fear of the unknown, which goes hand in hand with our desire to explore the world and the technology we develop to facilitate that exploration, which in turn generates its fears. As a result, I’ve chosen 50 of the best sci-fi horror films of all time for their distinctive, entertaining, and maybe even mind-blowing take on reality. Here we go!
50. Possessor (2020)
Possessor follows corporate assassin Tasya Vos (Andrea Riseborough), who utilizes brain implants to occupy the bodies of others and command them to execute killings in the name of the business for which she works. When the psychological consequences of Vos’ successful job as a puppeteer of surrogate killers begin to manifest, she is dragged into a complex web of sex, dualism, and realistic (and gory) visual effects. The possessor is a film that is brimming with wonderful ideas but never completely realizes or executes them.
49. Frankenstein (1931)
This film, directed by James Whale, is based on Mary Shelley’s renowned novel of the same name. This famous horror film follows Dr. Henry Frankenstein (Colin Clive) to create a life by constructing a monster from deceased body parts.
Frankenstein succeeds in animating his monster (Boris Karloff) with the assistance of his faithful deformed helper, Fritz (Dwight Frye), but the monster, confused and frightened, escapes into the countryside and begins wreaking havoc. Frankenstein seeks out the enigmatic creature and is finally forced to meet his troubled creation.
48. Brightburn (2019)
Tori Breyer’s parenthood aspirations come true with the advent of a mystery baby boy following a tough fight with conception. Brandon looks to be everything Tori and her husband, Kyle, could have wished for in a partner — intelligent, talented, and curious about the world. However, as Brandon approaches adolescence, a great evil within him develops, and Horrible concerns about her son torment tori. Once Brandon acts on his warped impulses, people closest to him face great peril.
47. 28 Weeks Later (2007)
Six difficult months after the heinous events of 28 Days Later… (2002), in which the unstoppable Rage Virus destroyed the entire city of London, the United States Army has restored order and begun repopulating the quarantined metropolis.
However, following the initial wave of returning refugees, one unwary carrier of the highly transmissible disease enters the lifeless metropolis, inadvertently re-igniting the fatal infection’s spread. Indeed, the virus is not yet eradicated, and it is more deadly than ever at the moment. Will the nightmare recur?
46. Underwater (2020)
A huge unknown earthquake strikes a drilling site in the Mariana Trench’s bottom. A research crew must navigate through the ocean floor to another station while facing dangers such as extreme pressure, murky water, deadly deep-sea animals, and a continual lack of oxygen.
45. The Invisible Man (1933)
A strange man with his head bandaged requests a room. The pub’s proprietors are used to converting their home into an inn during the winter months, but the guy is adamant. They quickly start to regret their choice. The man soon runs out of money, and, on top of that, he has a terrible temper. Worse still, he appears to be a scientist since his room is strewn with dirty chemicals, test tubes, beakers, and the like. When they attempt to evict him, they find a horrific discovery.
Meanwhile, Flora Cranley pleads to her father for assistance in resolving the mystery surrounding Dr. Griffin, his assistant, and her sweetheart’s absence. Dr. Kemp, her father’s other assistant, is of no assistance. He wants her just for himself. Flora has no idea that the crazy tales of an invisible homicidal madman from newspapers and radio broadcasts are the stories of Dr. Griffin himself, who has found the secret of invisibility and gone insane in the process.
44. Re-Animator (1985)
Herbert West is a Swiss scientist who discovers a fluid capable of reviving dead tissue in this H.P. Lovecraft novel. Following his professor’s mysterious death in Switzerland, West relocates to Miskatonic University to pursue his study. By experimenting on their deceased cat, he includes fellow student Dan Cain and his fiancée Megan Halsey in his investigation. Dan, taken with West’s study, agrees to smuggle him into the hospital morgue, resulting in predictable consequences.
43. Prometheus (2012)
Following a thin trail of evidence, acclaimed archaeologist Doctor Elizabeth Shaw and her colleague, Charlie Holloway, embark on an ambitious deep-space research mission with a seventeen-man crew. In 2093, aboard the ground-breaking space research vessel USCSS Prometheus, the team sets foot on the barren exomoon LV-223 to explore the presence of the superior alien civilization known as the “Engineers.”
However, other enigmas lie under a strange, complex edifice of enormous dark rooms and an elaborate underground network of tunnels. Now, a horrifying revelation jeopardizes not just the success of the audacious outer-space voyage but possibly humanity’s very existence. Is the world prepared for the answers to humanity’s core questions?
42. The Hidden (1987)
An extraterrestrial parasite capable of assuming human form goes on a violent crime rampage in Los Angeles, causing hundreds of murders and robberies. An FBI agent and a local police officer are on the lookout for the alien criminal. As they move up on the violent invader, the city faces an unprecedented level of violence.
41. The Island of Dr. Moreau (1996)
Dr. Moreau successfully combines human and animal DNA to create a crossbreed animal in the year 2010. As is customary, something goes wrong, and David Thewlis must act quickly to avert disaster. Originally classified R, Frankenheimer changed the rating to allow for “a broader audience.”
40. Planet Terror (2007)
In an abandoned military base in Texas, the gang led by black market trader Abby comes up against a squad of renegade soldiers led by Captain Muldoon. Abby shoots a receiver of a biological weapon during their gunfight, releasing an experimental, extremely infectious gas that transforms individuals into flesh-eating zombies.
Meanwhile, Dr. Block observes an outbreak at the local hospital, with several patients exhibiting the same dreadful symptoms. When the epidemic kills the majority of the local populace, a group of individuals with immunity, led by mechanic Wray, Sheriff Hague, stripper Cherry, and Dr. Dakota, the battle to live and become the world’s final chance.
39. Existenz (1999)
Allegra Geller, the world’s finest game designer, is conducting a focus group test of her new virtual reality game, eXistenZ. They begin with an attack on her by a crazed assassin using an odd organic pistol. She leaves with Ted Pikul, a young marketing trainee who is unexpectedly assigned as her security. Regrettably, her pod, an organic gaming device with the sole copy of the eXistenZ game software, has been damaged.
To investigate it, she convinces Ted to have a game port implanted in his own body, allowing him to play the game with her. The events leading up to this point and the subsequent game take the two on an odd trip in which reality and their actions are hard to discern from either their own or the game’s perspective.
38. Train to Busan (2016)
Survival is a matter of life and death on the train to Busan. Seok-woo, a divorced dad, is always pressed for time with his daughter Su-an. He offers to accompany her on the train to Busan to visit her mother. As the train departs, an odd virus spreads from an afflicted girl, and passengers begin to morph into zombies. Will Seok-woo and Su-an survive? TRAIN TO BUSAN is the feature film debut of filmmaker YEON Sang-ho, hailed by Cannes for his avant-garde animation.
37. Cube (1997)
Six individuals from disparate walks of life awaken to trapped inside a massive cube with hundreds of potential chambers. Each character has a unique ability that becomes apparent when they are forced to work together to escape: a cop, a math genius, a construction designer, a doctor, an escape master, and a handicapped guy. Each has a role to play in their fascinating journey to discover why they have been imprisoned.
36. Life (2017)
Six astronauts aboard the space station examine a Mars sample containing signs of alien life on the Red Planet. The team discovers a huge, single-celled creature in the sample – the first evidence of life beyond Earth. However, things are not always as they appear. As the crew conducts study and their methods have unexpected repercussions, the life form reveals far more sophisticated than anybody anticipated.
35. Vivarium (2019)
A young couple is considering purchasing their first house. And to that aim, they visit a real estate office, where they are greeted by an odd salesperson who takes them on a tour of a new, enigmatic, weird housing complex, where they are shown a single-family house. They become caught in a strange, maze-like nightmare while there.
34. The Meg (2018)
Deemed insane for claiming that a failed rescue mission in Philippine waters was doomed due to an apparently extinct predator of epic proportions—the prehistoric Megalodon—Jonas Taylor, the world’s greatest deep-sea rescue diver, finds himself five years later in the vast ocean realm of the Mariana Trench.
However, when three scientists from an underwater research station near Shanghai become stranded inside a broken submersible that has been attacked by an unknown beast, Jonas will need to act quickly to redeem himself. Could it be that the discredited rescuer’s beliefs about the deadly undersea leviathan are, in fact, true?
33. Bride of Frankenstein (1935)
Both Henry Frankenstein and his monster survive in this sequel to Frankenstein (1931). The monster, whom the local people believe to be dead, is discovered as he attempts to save a little girl from drowning. He is apprehended but flees into the woods, where he encounters a blind man who uses his violin to charm him.
Meanwhile, Dr. Frankenstein is compelled to collaborate with the insane Dr. Pretorius, who has been experimenting with the creation of life as well. When the monster ultimately returns to Frankenstein’s laboratory, Frankenstein and Pretorius build a lady to serve as his companion. When she rejects him, tragedy ensues.
32. Zombieland (2009)
Zombieland is a horror-comedy about two guys who have discovered a method to survive in a world overrun by zombies. Columbus is a wimp – but fear may keep you alive when you’re terrified of being eaten by zombies. Tallahassee is an AK-wielding, zombie-slaying badass who is hell-bent on capturing the last Twinkie on the planet.
As they join forces with Wichita and Little Rock, each of which has devised novel strategies for surviving the zombie apocalypse, they must decide which is worse: depending on one another or surrendering to the undead.
31. Island of Lost Souls (1932)
Edward Parker is abruptly left on an island belonging to Dr. Moreau after being rescued by a passing freighter when his ship sinks. He is made to feel comfortable there, though his host cautions him not to pass judgment on whatever he sees on the island too soon or harshly. Moreau has been performing genetic experiments on animals, transforming them into hybrids of man and beast.
While Parker is repulsed by what he has discovered, Moreau determines that he may be useful in some of his experiments. Meanwhile, Parker’s fiancée arrives on the island in an attempt to entice him back. Finally, Dr. Moreau must bear the cost of his experiments.
30. The New Mutants (2020)
Danielle Moonstar awakens at an abandoned research facility run by the mysterious Dr. Cecilia Reyes following a near-death experience during a bizarre tornado. There, Dr. Reyes introduces Dani to four other unusual teenagers: Illyana Rasputin, Rahne Sinclair, Sam Guthrie, and Roberto da Costa, who want to keep them safe until they learn how to fully manage their exceptional talents.
Despite the fact that the extraordinary team of traumatized convicts believes they are being treated and cared for, they soon begin to encounter terrible hallucinations. However, this institution was intended to be a secure environment. Are they patients, or are they detainees?
29. The Platform (2019)
In the future, convicts confined in vertical cells will observe as inmates in the higher cells receive food while those in the lower cells go hungry. Goreng reawakens in a section of The Hole, a location where food is delivered through The Platform. As the upper classes become more greedy and consume whatever they want, the lower classes gain less.
Goreng learns from his cellmates that the people below can succumb to lunacy and sanity loss, eventually resulting in brutal cannibalism, and so he begins devising a plan for The Hole’s inhabitants.
28. Color Out of Space (2020)
A cosmic horror novel about The Gardners, a family who relocates to a distant farmstead in rural New England in order to escape the 21st century’s rush and bustle. They are adjusting to their new existence when a meteorite collides in their front yard.
The enigmatic aerolite appears to dissolve into the soil, imparting a weird, unearthly hue to both the terrain and the characteristics of space-time. To their dismay, the Gardner family discovers that this extraterrestrial energy is progressively altering all living things it comes into contact with…including them.
27. Dark Skies (2013)
Terrible Skies, which premiered in 2013, addressed the often horrific phenomena of extraterrestrial visitations and abductions, in which a regular suburban family is targeted by an unknown alien presence with dark intentions for their children. As the Barrett family’s tranquil suburban existence is disturbed by a growing sequence of strange occurrences, they discover that they are being pursued by a terrible and lethal entity that may have arrived from beyond the stars.
26. The Faculty (1998)
Herrington High School in Herrington, Ohio, is a small-town high school. Teachers’ attitudes begin to shift abruptly. When Casey and Delilah are forced to conceal themselves in a closet in the teacher’s lounge, they see two of them strangling Nurse Harper. They manage to leave, stunned. Only seconds later, the nurse appears to be fully alive but also altered, much like the rest of the professors and the majority of pupils.
Casey, Delilah, and four others appear to be the only ones who are suspicious. The chemistry instructor eventually brings proof of an extraterrestrial virus, as well as a method of eradicating the afflicted people. The objective now is to capture the queen before the invaders take over the entire country.
25. Mimic (1997)
A new, highly contagious illness is wreaking havoc on Manhattan’s youngsters and has reached epidemic proportions. In despair, Peter Mann approaches Dr. Susan Tyler, an entomologist, and requests assistance in eliminating the disease vector, the common cockroach. Susan genetically creates a new predatory bug that will eradicate and eventually die off the cockroach.
Although this innovative approach works and the youngsters heal, nature is not a laboratory, and things do not always go as planned. Three years later, individuals begin to vanish, mutilated remains are discovered, and strange stories about gigantic insects imitating man begin to emerge among the bag people who live in the Manhattan underground system. Peter and Susan are summoned to assist with the investigation.
24. Annihilation (2018)
It has been twelve months since Kane’s last clandestine operation, and he remains missing in combat, believed dead. With his wife, Lena, still grieving his loss, an unusual phenomenon in the Florida swamplands will soon have her following in Kane’s footsteps as a member of a powerful all-female squad.
Numerous ideas have been proposed to explain the strange ever-expanding iridescent membrane that consumes the region; however, none have been proven. What tremendous are biological changes concealed behind this vibrant and colorful kaleidoscope of horrors? Finally, what did Kane observe?
23. Altered States (1980)
Edward Jessup, a renowned scientist and psychology professor, decides to mix his sensory deprivation tank studies with potent hallucinogenic substances in the hope of unlocking other realms of consciousness. At first, the tests are successful, but Jessup begins to experience changed mental and bodily states as a result of his work. His grasp on reality weakens as he spends more time in sensory deprivation.
22. A Cure for Wellness (2017)
A young, ambitious executive is dispatched to fetch his company’s CEO from a lovely but mysterious “wellness facility” in the Swiss Alps. He quickly develops suspicions that the spa’s miraculous treatments are not what they appear to be. When he begins to decipher its terrible mysteries, his sanity is called into question when he is diagnosed with the same strange ailment that has all the visitors here yearning for a solution.
21. Scanners (1981)
Darryl Revok is the most powerful scanner of them all and is the leader of the underground scanner movement seeking global dominance. Scanners possess tremendous psychic strength, sufficient to manipulate minds; they are capable of inflicting severe pain/damage on their victims. Doctor Paul Ruth discovers a scanner that Revok does not possess and convinces him to join their cause – destroying the subterranean movement.
20. Us (2019)
To unwind from their hectic life, the Wilson family travels to Santa Cruz, California, in order to spend time with their friends, the Tyler family. Their little boy Jason nearly runs away during a day at the beach, prompting his mother, Adelaide, to grow protective of her family. That night, four mystery guests break into Adelaide’s childhood house. The family is taken aback to see that the invaders resemble them, although with hideous looks.
19. Predator (1987)
A squad of special forces operatives, headed by a harsh but fair Major “Dutch” Schaefer, is sent to help CIA agent Colonel Al Dillon on a rescue operation for possible survivors of a helicopter that has crashed in the South American forest. Dutch and his crew quickly find that they have been sent in under false pretenses. This deceit, however, proves to be the least of their concerns as they discover themselves being stalked by something otherworldly.
18. The Mist (2007)
David, Steff, and their son Billy Drayton live in a tiny town in Maine. One night, a violent storm devastates the region, destroying their home. The following morning, the storm is followed by an odd mist. David, Billy, and Brent Norton venture into town and become stuck in a grocery shop with numerous other individuals. They find that the mist contains something terrifying that is hell-bent on annihilating humanity.
17. Videodrome (1983)
Max Renn, a sleazy lowlife cable TV operator, finds “Videodrome,” a snuff broadcast. However, it is more than a television program; it is an experiment in which viewers’ perceptions are permanently altered by brain damage caused by repeated television transmissions. Max gets caught in the crossfire between the powers that developed “Videodrome” and those seeking to control it, with his body becoming the ultimate weapon in the struggle against this worldwide conspiracy.
16. World War Z (2013)
When former United Nations investigator Gerry Lane and his family become trapped in metropolitan congestion, he knows something is wrong. His fears are verified as the city suddenly devolves into anarchy. A deadly virus, spread by a single bite, is transforming otherwise healthy individuals into violent, thoughtless, and savage creatures. As the epidemic threatens to engulf mankind, Gerry leads a global hunt for the infection’s source and, perhaps, a halt to its spread.
15. 10 Cloverfield Lane (2016)
Michelle awakens in a strange bunker with two guys called Howard and Emmett following a vehicle accident. Howard hands her a set of crutches to assist her in remaining mobile while recovering from her leg injuries received in the automobile collision and instructs her to “get good on those” before exiting the bunker.
She has been informed that an extraterrestrial attack occurred and that the outer world has been poisoned. However, Howard and Emmett’s motives quickly grow suspect, and Michelle is forced to consider the following: Is it better to be here or out there?
14. Cloverfield (2008)
A recording is discovered in the former Central Park by the US Defense Department. The film depicts a group of friends throwing a surprise farewell party at Rob Hawkins’ Lower Manhattan apartment. Rob is a young man leaving New York for Japan to work, and his pal Hud is recording messages from his buddies.
They are taken aback by an earthquake and learn via the news that a ship has capsized in the harbor area. They proceed to the penthouse to watch the disaster and observe explosions everywhere; when the building’s power goes out, they flee to the streets to avoid being attacked by the monster.
13. A Quiet Place (2018)
In a shattered Earth overtaken by unstoppable predators of unknown origin, the Abbotts struggle for survival in the bleak urban jungle of New York City, marked by a new period of complete quiet. Indeed, because this new species of the invader is drawn to noise, even the faintest sound may be lethal; yet, it has been twelve months since the formidable creatures were first spotted, and this tenacious family continues to thrive.
Naturally, mastering the laws of life in this muted dystopia is critical; nevertheless, today, more than ever, an otherwise joyful occasion jeopardizes the already precarious equilibrium. And now, maybe more than ever, the Abbotts must remain silent.
12. The Terminator (1984)
Sent back from a future 2029–where icy machines have dominated the world—to 1984 Los Angeles, the indestructible cyborg-assassin known as the “Terminator” begins his lethal mission to assassinate humanity’s most important woman: the unsuspecting Sarah Connor.
However, from the same war-torn post-apocalyptic future emerges a battle-scarred defender—Kyle Reese, a valiant soldier of the human Resistance Army—dedicated to preventing the cybernetic murderer from killing the world’s final chance. However, the Terminator is emotionless, he does not sleep, and most importantly, he will not stop until he completes his heinous mission. Is our future entwined with our past?
11. A Quiet Place Part II (2020)
With the newly discovered vulnerability of the supposedly invulnerable animals, grief-stricken Evelyn Abbott finds herself alone, with two young teenagers, a defenseless newborn son, and nowhere to hide. Now, 474 days after A Quiet Place (2018)’s all-out alien invasion, the Abbotts muster every ounce of bravery to flee their now-burned-to-the-ground farm and start on a perilous trek to locate civilization.
With this in mind and desperate to push the boundaries, the tenacious survivors are forced to go into the eerily calm, unexplored hazardous area in the hope of a miracle. However, the adversary is everywhere this time.
10. Invasion of the Body Snatchers (1978)
Matthew Bennell, a public health inspector in San Francisco, is interested when a coworker and personal friend, Elizabeth Driscoll, informs him that her husband has changed dramatically. He advises they consult with his buddy, psychiatrist David Kibner, who agrees that some of his patients say their husbands or spouses are not who they appear to be.
He chalks it up to widespread hysteria until two other friends of Matthew’s, Jack and Nancy Bellicec, uncover a partially formed body. They quickly learn that people are being displaced by perfect replicas, which are heartless and appear to be unstoppable in their mission to supplant everyone.
9. The Fly (1986)
Seth Brundle (Jeff Goldblum), a bright but eccentric scientist, seeks to seduce investigative journalist Veronica Quaife (Geena Davis) by giving her a scoop on his newest study in the realm of matter transportation, which has proven effective against all odds. Until a certain point.
Brundle believes he has resolved the last issue when he successfully transfers a living thing, but when he tries to teleport himself, a fly enters one of the transmission booths, and Brundle discovers he has changed. The quotable statement is from this Science-Gone-Mad flick “Be fearful. Be quite scared.”
8. Event Horizon (1997)
The year is 2047, and a spacecraft called the Event Horizon has resurfaced seven years after missing during trials with faster than light travel. A rescue craft is hurriedly dispatched to the returning vessel after a garbled communication from the ship was picked up, loosely like a human voice. As the crew reaches the ship and spends more time aboard, it looks as though someone or something is toying with them, and the question becomes what has become of the Event Horizon.
7. Hellboy (2004)
When the Nazis seek to utilize black magic during the final days of World War II, they summon a monkey-like monster. Trevor “Broom” Bruttenholm discovers and rescues the creature. When the monster matures, he adopts the moniker “Hellboy.” Hellboy works in secret to eradicate all evil. When certain old figures from Hellboy’s past reappearance, it will take more than Hellboy to put an end to them.
6. Pitch Black (2000)
When a meteor shower strikes the transport ship “Hunter-Gratzner,” pilot Carolyn Fry awakens from cryogenic hibernation and attempts to control the vessel’s forty passengers. Carolyn, the bounty hunter William J. Johns, the pious Abu “Imam” al-Walid, the dealer Paris P. Ogilvie, Sharon ‘Shazza’ Montgomery, the runaway adolescent Jack, John ‘Zeke’ Ezekiel; Suleiman; Hassan); Ali and the deadly criminal Richard B. Riddick survive.
Riddick flees, and Johns warns the survivors of his threat. The party becomes stuck in the desert and discovers that the area is heated by three suns, prompting them to band together in search of water and supplies. They soon find that the planet is under assault by flesh-eating aliens that strike in the dark; moreover, the world will be completely dark due to a total eclipse. They decide that they need not be concerned about Riddick.
5. Bird Box (2018)
In the midst of a nightmare new reality in which an invisible malicious entity is purging the entire population, Malorie and her two children go on a perilous trek to discover the only safe refuge on Earth. However, in this perilous journey, one’s eyesight is the true adversary—and as the defenseless blindfolded guardian musters the strength to pursue a tiny glimmer of hope buried deep in a riverside shelter, darkness may be the only thing that may save them. Now, the survival rules have shifted. Will Malorie and her children make it to the end of the day?
4. Slither (2006)
A blazing meteorite crashes from the depths of infinite space into the dark woods of the peaceful hamlet of Wheels, South Carolina. As the charred rock reveals its hidden content—a heinous parasitic organism—a stealthy extraterrestrial invasion begins, with Grant, the town’s unlucky first victim.
Gradually, as an internal transformation changes, Grant into an absolutely monstrous creature, his wife, Starla, begins to sense that something has been eating away at him for the previous few days. No one is safe now, in the face of an unrelenting alien onslaught, and to make matters worse, Grant’s metamorphosis is far from complete. Who is capable of putting an end to the creeping army from outer space?
3. The Thing (1982)
A scientific trip by an American to the Antarctic’s icy wastes is disrupted by a bunch of obviously insane Norwegians following and shooting a dog. The helicopter following the dog explodes, thereby ending the hunt. Throughout the night, the dog mutates and attacks the other canines in the cage as well as members of the investigation team. The crew quickly discovers that an alien life form capable of taking over other bodies is on the loose, and they have no idea who may have already been taken over.
2. Alien (1979)
The crew of the commercial spacecraft Nostromo is returning home in the far future when they pick up a distress call from a distant moon. The crew is obligated to investigate, and the spaceship then lowers to the moon. Following a difficult landing, three crew members depart the spaceship to investigate the moon’s surface.
Simultaneously with discovering an unknown creature’s hive colony, the ship’s computer deciphers the message as a warning, not a distress cry. When one of the eggs is disturbed, the crew discovers they are not alone aboard the spacecraft and must cope with the ramifications in the Alien.
1. Aliens (1986)
Lieutenant Ellen Ripley is the only survivor of a far-future alien attack on her ship, played by Sigourney Weaver in the film. When communications are lost with a human colony on the moon on which her crew first encountered the alien creatures, Ripley agrees to return to the site with a troop of Colonial Marines to investigate. Aliens feature Michael Biehn, Paul Reiser, Lance Henriksen, and Carrie Henn in supporting roles.