LOS ANGELES (REUTERS) - The ninth film in the original Star Wars saga will be called The Rise Of Skywalker and will see the return of the evil emperor Palpatine to threaten the young heroine Rey and the Resistance, Walt Disney revealed on Friday (April 12).

Disney showed fans at the Star Wars Celebration convention in Chicago the first footage from the movie, which will be released in theatres in December and will conclude the saga that began in 1977.

A villainous cackle was heard at the end of the trailer, and the actor who played Palpatine in previous films, Ian McDiarmid, walked on stage to loud applause from an audience of roughly 10,000 fans, many waving colourful lightsabers.

Director JJ Abrams, speaking alongside many of the film's stars, said the movie takes place some time after the events of 2017 film The Last Jedi.

The footage showed a hug between Princess Leia, played by the late Carrie Fisher, and Rey (Daisy Ridley). Fisher died in 2016, but Abrams said that in a "weird miracle" he was able to piece together unused footage from Last Jedi to continue the beloved character's story.

"She's so alive in the scenes," Abrams said. "Princess Leia lives in this film in a way that's mind-blowing for me."

The circumstances surrounding Palpatine's return remain a mystery. The character appeared to be killed in the 1983 film Return Of The Jedi.

In the trailer released on Friday, the voice of Luke (Mark Hamill) tells Rey that "no one's ever really gone."

Luke also tells Rey that "we have passed on all the knowledge" and that the fight against evil is now hers.

Ridley appeared with John Boyega, who plays Resistance fighter Finn; Oscar Isaac, who portrays pilot Poe Dameron; and others, bringing fans to their feet.

The largest ovations came for Kelly Marie Tran, who portrays mechanic Rose Tico, and Billy Dee Williams, who returns to the saga as the con artist Lando Calrissian. Williams last played the character on-screen in 1983.

"Lando never really left me," Williams said to applause.

Disney introduced a new character named Jannah, portrayed by Naomi Ackie. The actress said she could not confirm or deny speculation that Jannah was Calrissian's daughter.

A new droid, D-O, pronounced "Dio," rolled onto the stage, joining BB-8 and R2-D2.

Abrams revealed little about the plot of The Rise Of Skywalker.

"This movie is about this new generation, what they've inherited, the light and the dark, and are they ready?" he said.