There is absolutely no doubt that George Lucas's venture into the fantasy space opera genre was a high-risk, high-reward situation, and luckily in May of 1977, it all proved to be worth it, with Star Wars becoming a worldwide phenomenon. There are so many brilliant elements to those first three movies that have kept them in the pop culture conversation and in fan's minds over forty years, many of which often do not get the appreciation they deserve.
These elements include the production design, effects, and costume/make-up of the trilogy, which all do outstanding work bringing a plethora of species to life. Some of their work results in iconic aliens and beloved creatures, but also some that can fear-inducing, creepy, and, for younger audiences, downright terrifying.
Gamorrean
In all honesty, the Gamorreans are not totally terrifying and, over time, become pretty funny to look at once you realize how little harm they actually cause our heroes.
Nevertheless, from a sheer design perspective, pigs have never looked so scary. For children watching the original trilogy for the first time, Jabba's Gamorrean guards are undoubtedly a scary sight with their slimy face, tusks, and lumbering beastly figure. They may be stereotypically dumb and fairly harmless, but there is an element of initial fear there.
Exogorth
Far scarier, with the surprise factor on its side, is the Exogorth, more affectionately known as the space slug from Han falls for, before making a daring escape.
The thing is just a giant space slug, which may not sound terrifying, but when it lures you into its stomach and is such a colossal size, as well as being just a nasty-looking customer, it does get you thinking about which craters you fly into.
Tusken Raider
Tusken Raiders, informally known as sand people, are one of the first alien species and natives to Tatooine fans meet in all of Star Wars, and they immediately make their presence felt.
Ambushing Luke is bad enough, but Obi-Wan makes the Tusken Raiders seem more frightful as he describes them as running in big numbers and being pretty manic in their attacks. Their look is frightening, with their mask adding an air of mystery to them and their cycler rifle and gaderffi stick adding to their aura.
Devaronian
The A New Hope introduced fans to a slew of weird and wonderful species of the Star Wars Galaxy, including the devil-like Devaronian, who is definitely one of the more frightening of the bunch.
With red skin, horns, and pointy teeth, the male Devaronian is a pretty terrifying sight. In contrast to their male counterparts, females are a lot less terrifying, but they also are not seen in the trilogy, only the males, earning the species a spot.
Trandoshan
The Empire Strikes Back introduced a slew of phenomenal characters to the Star Wars fandom, not least of all the group of bounty hunters hired by Darth Vader, with the most intimidating species-wise being, by far, Bossk.
As a Trandoshan, Bossk is made far scarier by hindsight. Just by looks, he is like a big, strong, reptilian humanoid with scary eyes and sharp teeth, but that may not be enough to earn Trandoshan's a spot here. What does, though, is the lore that goes along with them. Famously, ruthless hunters who enjoy killing for sport, Trandoshan's are bloodthirsty, violent beings, which helps Bossk's career while also making Trandoshan's one of the scariest species seen in the trilogy.
Mynock
Sticking with what many feel is the best movie the Skywalker saga has to offer, the Exogorth is not the only dangerous and frightening creature Han and company run into on the Falcon, with the Mynock's producing a horror-esque scene; on the inside, the latter nonetheless.
Scary creatures that fly are one thing, but what makes Mynocks more chilling is their parasitical nature. Mynocks could drain the power supplies of ships, even getting 'drunk' on the energy from them. They also reproduced by simply splitting in two and growing new creatures from each half, all of this information making them more and more creepy. On the positive for those who do get freaked out by the bat-like parasites, they are seen as a delicacy to some carbon-based species (only when seasoned properly.)
Dianoga
Speaking of horror-esque moments, another one comes in A New Hope and is the first one of the trilogy, taking place in the famous trash-compactor scene where something pulls Luke into the waste.
This creature, seen only by its eye and a glimpse of its body, was a Dianoga, perhaps the creepiest creature on this list. They are deceptively big, with seven tentacles, multiple hearts, razor-sharp teeth, and lived primarily underwater. However, the Dianoga, specifically from A New Hope, is far less frightening after reading From A Certain Point Of View, where the Dianoga gets her own story and a name, Omi.
Sarlacc
ittedly the Sarlacc has gone down in of the blood-curdling fear it has the potential to put into people, mainly due to the design. Nevertheless, it remains an objectively nerve-racking creature.
Perhaps the most dreadful aspect of the Sarlacc is the fate of its victims. For those unfortunate enough to find themselves in the mouth of the beast, they are injected with neurotoxins, leaving them immobile yet conscious and in extreme pain as they are digested over a millennium.
Wampa
Topping previous entries on the horror-esque factor is the spine-chilling Wampa attack on Hoth at the start of The Empire Strikes Back, where it looked like Luke was in serious danger.
The entire sequence produced the iconic image of Luke using the Force to get his lightsaber to save himself, but more daunting images are the blood-covered, yeti-like being eating his food with his fangs and eyeing up our protagonist like a slab of meat.
Rancor
Arguably the best monster-scene in Star Wars comes in Return Of The Jedi in Jabba's Palace when he sends Luke to the pit underneath his main hall to fend off one of his favorite pets, the Rancor.
While Luke intelligently deals with the beast, that does not take away from how intimidating it is. With armored hides, huge jaws, strong, sharp teeth, and giant claws, the Rancor may move slow, but it could still easily leave anyone in a state of shock at the sheer sight of it.
