Army of Darkness is the third film in the Evil Dead film series, released in 1992.
After the events of Evil Dead II, Ash time travels to the Middle Ages, where the people try to execute him, but a Wizard gives him his chainsaw hand, and kills the monster that was going to kill him.
After proving himself, the people now trust him, and the wizard asks Ash to retrieve the Necronomicon, so they can stop the evil from spreading, but he has to say a spell before taking the book.
Ash gets the book, but says the spell incorrectly, and unleashes an army of Skeleton's, known as the Deadites. An evil version of Ash leads the skeleton army to the castle so he can snatch the book, luckily, Ash and the people of the castle join forces with another kingdom, and they battle the undead army.
After their victory, Ash returns to his own time, but he still continues to battle the evil dead.