1. "All Souls" (Season 5, Episode 17) Tap to play or pause GIF Tap to play or pause GIF FOX / Via iheartthexfiles.com When special needs girls from a quintuplet birth start dying in a mysterious manner that has strong religious overtones, Scully starts looking for an answer in her faith. She finds similarities between the girls and the Nephilim, and the agent realizes that she is battling an ancient and powerful evil hell-bent on taking the girls' souls. This episode might not have a traditional fright factor, but the demonic aspect is especially eerie. 2. "The Calusari" (Season 2, Episode 21) FOX / Via pinterest.com A couple's toddler gets hit by a train and then his father is found dead. Scully and the mother suspect the grandmother, who is extremely superstitious and known to perform strange rituals. However, when she points the finger of blame at Charlie, the other child, the grandmother dies under mysterious circumstances. There's just something wonderfully spooky about killer children and a good old fashioned exorcism. 3. "Sanguinarium" (Season 4, Episode 6) Tap to play or pause GIF Tap to play or pause GIF FOX / Via hypatiaswrath.tumblr.com A patient is seemingly murdered by a plastic surgeon during a routine operation, who later claims he was possessed. Mulder suspects witchcraft due to a pentagram found at the site of death, and his fears are confirmed when another patient is killed in a similar manner. As the bodies begin to pile up, a larger conspiracy is revealed. The horrific "surgeries" and theme of witchcraft make this episode pretty freaky. 4. "Chinga" (Season 5, Episode 10) FOX / Via smallthingsdefine.tumblr.com When Scully tries to go on vacation, she witnesses a bizarre event that derails her plans. While law enforcement and the townspeople point fingers at a mother, whom they accuse of witchcraft, Scully realizes that her child's doll is actually the culprit. Even though this is not the most popular episode with fans or critics of the show, "Chinga" is written by Stephen King and deserves to appear on this list for that reason alone. Plus, it's incredibly scary for anyone who's afraid of dolls. 5. "War of the Coprophages" (Season 3, Episode 12) Tap to play or pause GIF Tap to play or pause GIF FOX / Via robots-aliens-monsters-ohmy.tumblr.com Tap to play or pause GIF Tap to play or pause GIF FOX / Via robots-aliens-monsters-ohmy.tumblr.com Tap to play or pause GIF Tap to play or pause GIF FOX / Via robots-aliens-monsters-ohmy.tumblr.com While investigating UFOs, Mulder is runs into a local sheriff who tells him that cockroaches have been killing people in the area. An entomologist working at a government testing site informs Mulder that she believes the UFOs are caused by the cockroaches. When a roach skeleton is found to be made out of metal, things start to get especially weird. "War of the Coprophages" has its funny moments, but I find that there's hardly anything more spine-tingling than large masses of cockroaches invading homes and killing people. Cockroaches are disturbing enough without all the killing. 6. "How the Ghosts Stole Christmas" (Season 6, Episode 6) Tap to play or pause GIF Tap to play or pause GIF FOX / Via unusual-disaster.tumblr.com Though this is technically a Christmas episode, is does take place in a haunted house. When Mulder and Scully enter the house, odd things begin to happen. They soon learn that they're being taunted by two ghosts, played by Lily Tomlin and Ed Asner, who try and prevent them from getting out alive. "How the Ghosts Stole Christmas" is great for anyone who likes a little humor with their spook. 7. "Folie a Deux" (Season 5, Episode 19) Tap to play or pause GIF Tap to play or pause GIF FOX / Via jillsandwich.tumblr.com Tap to play or pause GIF Tap to play or pause GIF FOX / Via jillsandwich.tumblr.com Tap to play or pause GIF Tap to play or pause GIF FOX / Via jillsandwich.tumblr.com Mulder and Scully are assigned to do a threat assessment when an unstable office worker, Gary, produces a manifesto which states that a monster is terrorizing employees. As the man takes his co-workers hostage, Mulder walks in and Gary slowly explains that his boss has been turning people into zombies. The creep factor in this episode is especially high because for most of it you're not really sure if Gary is insane or if there really is a giant bug monster that makes zombies. 8. "X-Cops" (Season 7, Episode 12) FOX / Via chrisnu.com This episode is an honest-to-god crossover between The X-Files and COPS. Though "X-Cops" is pretty hilarious, it's also very scary at times because it's shot in the style of COPS which makes it seem more realistic. Mulder and Scully make their appearance after a series of strange sightings and attacks in the area. When conflicting eyewitness reports all point to different attackers, Mulder must abandon his werewolf theory and focus on finding something much more frightening. 9. "Irresistible" (Season 2, Episode 13) Tap to play or pause GIF Tap to play or pause GIF FOX / Via hugatreeortwo.tumblr.com Mulder and Scully are called in when a body desecration looks like the work of aliens. Mulder points the finger at an escalating fetishist who might soon turn to murder. When he does, Scully starts having nightmares about the case and it's revealed that she is his next target. There's nothing much creepier than a serial killer who has a deep affection for hair and fingernails. 10. "Die Hand, Die Verletzt" (Season 2, Episode 14) FOX / Via diehand-dieverletzt.tumblr.com The biggest theme in this episode is Devil-worship, making it especially perfect for Halloween. Mulder and Scully are called in when a boy is murdered during a ritual he and his friends do in the woods. It turns out that the school board is comprised of active Satanists who have been slacking on their worship. The ritual that the teenagers perform actually releases the Devil, who begins to take revenge on the board in the form of a substitute teacher. 11. "Badlaa" (Season 8, Episode 10) FOX / Via realityimpaired.tumblr.com A business man is dragged out of a bathroom stall before boarding a flight to DC. He's found dead in his hotel room, but the time of death leads Scully to believe something supernatural is afoot. Other deaths begin to happen, and people close to the deceased report seeing a little man with no legs pushing himself around on a cart. This man is no doubt one of the creepiest characters ever introduced to us by "the X-Files." 12. "Squeeze" (Season 1, Episode 3) Tap to play or pause GIF Tap to play or pause GIF FOX / Via littledivinity.tumblr.com Tap to play or pause GIF Tap to play or pause GIF FOX / Via littledivinity.tumblr.com After several victims are discovered with their liver removed and no feasible point of entry for the murderer, Mulder zeroes in on an abnormally long fingerprint found at the scene of the latest death and connects it to a series of X-Files. While Scully refuses to believe that it is possible, Mulder begins looking for a man who's over 100 years old, and is able to squeeze his body into tight spaces in order to procure his victims. Though this is one of the earliest episodes, it's definitely one of the creepiest. The idea of a killer who can get to you through spaces even a cat couldn't fit through is very disconcerting. 13. "Home" (Season 4, Episode 2) Tap to play or pause GIF Tap to play or pause GIF FOX / Via allxfiles.tumblr.com Tap to play or pause GIF Tap to play or pause GIF FOX / Via allxfiles.tumblr.com Probably the most whacked-out episode of "The X-Files" ever made, "Home" follows Mulder and Scully's visit to a rural town after a newborn's body is discovered. The culprits are quickly identified as the Peacocks, a family that's been inbreeding for several generations and loathes the outside world. This episode will definitely make you think twice about living in the country.