The "Kandarian Demon" is an ancient demonic spirit that can possess anyone with its mere touch, in its present state, it is an incorporeal evil spirit, a poltergeist of sorts with the supernatural ability to interact with objects in its vicinity. Furthermore, they have the power to possess a host, to assimilate them into a Deadite form. The demonic spirit appears in all of the Evil Dead films including Army of Darkness and the Evil Dead video games as well as many other related items (except in the reimagined Evil Dead, which it replaced by Taker of Souls aka Shaitan with similar powers albeit at an inferior scale). The Kandarian Demon is usually portrayed by POV (point of view) cameras as an entity that roams about in the woods. Kandarian seems to have control over objects surrounding it such as trees, vines, and other objects as well as being able to infuse them with flesh and blood.
A "Deadite" being a person, animal, or any being with a soul, possessed by the Kandarian Demon and it's fellow spirit thralls.
Origins
The origin of the Kandarian Demon (or just 'Kandarian') may be traced back to a time predating the age in which the Necronomicon Ex Mortes a.k.a. Naturum Demonto, the original Book of the Dead, had been written by the Dark Ones. According to Professor Ed Getley, the book was written roughly 3.000 years before 1987, or maybe even more than that (as suggested by Annie Knowby).
The book was written in the Ancient Sumer, when the seas "ran red with blood". Presumably, the Dark Ones were gifted people bearing supernatural capabilities and dealing with outerdimensional creatures and demons running on Earth. In the attempt to exert command upon these demons and thus having some kind of supremacy in the world, they created the book as a way to channeling some of these obscure forces and putting them in check the best way possible.
Long before the book, Kandarian's were running amok. It was a Living Evil born in the "space between the spaces", an interdimensional demon world. Many events could have brought the creature to lose its "life" and become "incorporeal" forever (apparently). In that specific time, The Evil Dead had (re)born with an hunger for life, a vital energy once lost. The Dark Ones found the right phonetic incantations to either make the entity dormant and forbid its terrible influence on human kind or awake it and bring destruction and horror. A chance to tame the beast and use it.
As explained by Dr. Raymond Knowby: "The book speaks of a spiritual presence. A thing of evil that roams the forests and the dark bowers of man's domain. It is through the recitation of the book's passages that this dark spirit is given license to possess the living".
Throughout centuries and millennia, new versions of the Book of the Dead were written, not with the best intentions. This caused some inconsistent variations in the way the Evil Dead interacted with the living world and our dimension.
The second biggest (multiple) manifestation of the Evil Dead had been in the 13th/14th century in Great Britain, involving the Kandar Castle. It was a ferocious battle between good and evil lasting decades. It was a pivotal moment in history. In the end, The Evil Dead was defeated and all Books of the Dead disappeared from Man's scenario. Until the 1970s.
Possession and Feeding
Basic victims and 'Possession'
In order to feed itself and amplify its demonic powers on reality, the Kandarian Demon needs the consumption of a soul and thus nourish its primordial existence.
Souls can be obtained in two ways: violent death of the individuals (TED Archeologist, Dr. Knowby, Bobbie Jo) usually dealt by a Deadite or by possession (the Deadites).
Once evoked through any of the Books of the Dead, they first must "feed" on the people who recited or just made the incantations "be listened to" in some way (tape recorder). Then, they can subsequently feed on the people who are located in the place where the incantations have been recited (see Annie & the ED2 company) if someone from the original batch is still alive (Ash in ED2). It's a sort of "cycle" the Kandarian Demon must fulfill.
If the number of souls absorbed is somehow limited, then the Kandarian Demon falls in a semi-sentient state, like sleepwalking. Under that modality, it can still interact with the surrounding reality to a certain extent (the very beginning of TED), albeit with no full consciousness or license to possess beings. Generally speaking, the Kandarian Demon spends the vast majority of its existence on Earth as a dormant entity.
On slumber mode, they can still "influence" some gifted individuals (like Cheryl who seems to own a mild E.S.P. ability). Said individuals, once possessed, present their latent abilities enhanced to the nth degree (Deadite Cheryl).
Once the Evil Dead has consummated an adequate number of souls, it can overcome its geographical limits and the "attraction" of the place where it has been evoked and take over the whole world, it also loses some of is weakness such as sunlight, as after possessing numerous souls in 1300 AD, it was able to roam and chase Ash during the day.
Aspect
The Kandarian in its incorporeal state seems to be surrounded by fog or indeed could be the fog given that the fog receded in an unnatural manner once the sun came out. Despite looking like fog or being masked by it, people are able to see it given how they always flee from it upon seeing it and it still possesses great strength in this form, being able to send an oncoming car flying into the air.
The Force,in its flesh manifestation
Once manifested in a solid form through the incantations of the Necronomicon Ex Mortes, the Evil Dead transforms into the Rotten Apple Head creature, a composite patchwork organism in which flesh interacts with vegetal elements. The actual souls the Evil Dead was recently "feasting upon" materialize under the form of human faces with deadite eyes embedded into the left side of the Head, including Ash after he had been possessed twice, it is unknown if the host souls are actually needed to be consumed for their faces to appear on the Kandarian given how Ash is still fully human with no sign of any permanent harm. The kandarian is vulnerable in its corporeal form, able to be physically harmed and sucked into a vortex. It is possible that the demon loses its ability to possess the living in its corporeal form as Ash wasn't possessed despite being in constant contact with Kandarian i.e he was in its grip.
History
The Evil Dead
Before the tape recordings that gave the Kandarian Demon the opportunity to possess the living were played in this film, the Kandarian alone was shown at the beginning of the film, roaming about in the woods and nearly causing the car containing the main characters (Ash, Scotty, Linda, Cheryl and Shelly) to crash, by causing the steering wheel to jerk out of Scotty's control which nearly caused a collision with an oncoming truck. Thus, even though it had not the power to possess people yet (presumably in weak condition or locked in another other world until unleashed), the demon was still alive and searching the forest. At that moment (The Evil Dead), the Kandarian was able to collapse trees that were in its path as it glided across the ground. Apparently, it also destroyed the bridge that served as the only way (until a hiking trail was discovered later) to get to and from the cabin, thus trapping the characters from leaving. In this same film, the Kandarian (once unleashed by Scotty's reading of the Necronomicon), is finally wholly free and uses this opportunity to possess Cheryl and then proceeded to possess the others.
Ultimately at the end of the film, Ash was caught by the Kandarian itself after it's hosts and a Necronomicon were presumed to be destroyed.
Evil Dead 2
In Evil Dead 2, the Force was spoken of by Professor Knowby as "a thing of evil" and a "dark spirit". The Kandarian also played a major role in the ending of the film. In the ending of the film, Annie and Ash had discovered two passages from the pages of the Necronomicon that they could use to dispell the Force. In order to do so, they needed to first recite an incantation that would cause the demon to take on a physical form, and then recite an incantation to open a vortex to suck the demon into a rift, apparently back in time. When the first passage was recited, the demon tried to break its way through the front door of the cabin and it appeared as a fleshy disembodied head with large teeth. Additionally, it was covered in the faces of its victims. Ash was able to damage the beast's eye with his chainsaw. The Kandarian was sucked back into the rift along with Ash, preceding the events of the next film, Army of Darkness.
Army of Darkness
Main article: Evil Ash
The Kandarian only played a short role in a chase sequence in it's normal form where it chased Ash through the forest, curiously in daylight (likely because it was in the full force that enable it to withstand sunlight). It was able to cause several trees to split in half in order to clear its path as it chased after Ash. Though failed, it later possessed a mirror and manifests as tiny Ashes where one of them managed to entered Ash's mouth, resulting the birth of Evil Ash, Ash's deadite clone that serve as it's physical extension to control the Deadite Army.
Ash vs. Evil Dead
The Kandarian Demon is once again accidentally summoned by the drunken and stoned Ash after a recent Marijuana-addled "poetry read" with another girlfriend where he mistook the summoning incantation in the Necronomicon as poetry. It went on to possess the girlfriend and Agent Fisher's partner before it went around possessing whoever was in its path. The Kandarian attempts to attack Ash and his friends on the road but the team manage to pass over onto sacred ground where the demon couldn't pass.
After the Delta is stolen, the necronomicon is read by one of the thieves, unleashing the demonic force once again. It possess the woman that read the book as well as the car itself and goes on a rampage that leads to Brock Williams' death.
Video Game Appearance
Evil Dead: Hail to the King
In the Evil Dead video game Evil Dead: Hail to the King, the Kandarian was shown via POV cam at the beginning of the game. When summoned, it broke through the window and took Jenny (Ash's girlfriend) somewhere instead of possessing her.
Evil Dead: Fistful of Boomstick
In the Evil Dead video game Evil Dead: Fistful of Boomstick, it was shown that nearly all Deadites had the incorporeal form of the Kandarian before possessing a victim.
Evil Dead: Regeneration
In the Evil Dead video game Evil Dead: Regeneration, the Kandarian was once again composed of many individual demonic spirits and appeared as glowing blue skulls with small horns and a glowing blueish-whitest tail. Its is unknown however if the Kandarian was ever the only one of its kind of if there indeed more of them, the demonic spirits shown in this game do take on the form of fog or mist as the Kandarian is revealed to do in Dead by Dawn and Ash vs. Evil Dead.
Trivia
- While the incorporeal form has been seen before in Evil Dead 2 when the fog recedes, most people could have considered this merely as fog, however, in the fourth episode of Ash vs. Evil Dead, its incorporeal form is shown properly and is indeed the fog itself.
- The Kandarian Demon has a cameo (in its first-person perspective) in Scary Movie, a horror spoof. It goes to a cabin and possesses the people there, causing them to self mutilate.