Deadite

The Deadites are the main antagonists of the cinematographic saga titled The Evil Dead. They are undead creatures controlled by the powers of both the Necronomicon Ex-Mortis, which is created by the hands of the Dark Ones, and of the Kandarian Demon. They have the power to possess the living and the dead, and are supporting major antagonists in the Evil Dead series.

Events in Film Series
The Deadites were released alongside the Kandarian Demon when Professor Knowby recited passages from the Necronomicon out loud. From then on, Ashley "Ash" Williams battled the Deadites that are hellbent on taking over the world and killing all living things including humans, where their very first victims were Ash's friends and his sister.

Ash vs. Evil Dead
By the events of Ash vs. Evil Dead, Ash recalls being with a recent female acquaintance and opening the Necronomicon when she pushed him to recite some poetry. When Ash recited the words from the cursed tome, the Deadites made their return. When State Trooper Amanda Fisher and her partner investigate reports of paranormal activity at an old house, they are attacked by the first wave of the Deadites. Fisher survived though her partner killed in the ensuing fight.

At first, Ash decided to behave normally to avoid unwanted attention, but was finally forced to tell the truth on his friend Pablo after an incident with the Deadite-possessed doll which mutated into a small but dangerous monster which Pablo smashed. Another wave of Deadites attacked, and with him the only one whom know better how to deal with the threat, Ash and his allies went to war against the demons.

Evil Dead remake
See: The Taker of Souls

In Evil Dead, the Taker of Souls is capable of conjuring and controlling its own Deadite thralls. Unlike regular Deadites however, these Deadite strains are less comedic, zombie-like, and masochistic in behavior, prone to harming oneself before attacking others. Owing to this, they are also quite resilient to injuries.

Behavior
In general, Deadites have a comedic but sadistic side and they are very dark-hearted beings, albeit with angry and childish moods. But they are not stupid or clumsy, as each of their minds are connected with a hive mind (the Kandarian Demon who leads them). They are also known for speaking "Engrish" (the grammatically incorrect English) at times.

As the series progresses, they developed a strong hatred towards Ash Williams, for him being the Chosen One and therefore, the only known man who endured their even most unpleasant torments (they did manage to mentally scar him for a time though). This in turn, allowed Ash to hone his skills in combating the dark forces they and the Kandarian Demon threw against him. As arrogant and treacherous as they can be, their fearful and cowardly side will surface if anyone gets their hands on the Kandarian Dagger (the only thing that can effectively kill them) or the Necronomicon itself. It's evident that they are obsessed more in the Necronomicon-Ex Mortis, as it is the only thing that can summon and control/enslave them.

Powers and Abilities
The Deadites are capable of possessing other people's bodies, and consuming their souls for a hobby or when there just being annoying to the person that read or pressed play on the tape recorder with the words from the Book of the Dead itself, to release the demon spirits from beyond and begin these spirits' possession over the unsuspecting mortals and their hunger for the flesh. Aside from possessing the living, Deadites in spirit form are capable of tossing around living people as if they are bales of straws, as demonstrated by the fog form of their collective intellect, the Kandarian Demon.

As shown in The Evil Dead and The Evil Dead II, the Deadites are capable of reverting their hosts back into their human form as an attempt to trick and lure their victims in addition of levitation and enhanced strength. As creatures of darkness, they are aversive to sunlight, since a particular Deadite spirit who possessed Ash at the beginning of The Evil Dead II was forced to release its hold over him. All the fog (which concealed the Kandarian Demon itself) throughout the forest disappeared. Should they possess the deceased, the Deadites can evolve into a much more powerful, horrifying form.

Weakness
Aside from the Kandarian Dagger and sunlight, the most effective method in killing Deadites is by severely damaging their physical form and/or host, typically via dismemberment, owing to the fact that mutilated corpses are useless for their possession. However, as revealed in Season 3 of Ash vs. Evil Dead, when body parts are reattached, Deadites can revive so once dismembered they must stay dismembered.