Though each Star Wars film has a proclaimed significance of its own, Star Wars: The Last Jedi hints at a brush with the dark side of the Force for its hero Luke Skywalker (Mark Hamill) and a heart-crushing final scene for its heroine General, nee Princess, Leia (Carrie Fisher).

For those reasons the film - the eighth, penultimate story in a nine-story that now spans four decades of filmmaking - has a particular significance for fans of the franchise who have been there since Star Wars rewrote the rulebook on cinema in 1977.

Make no mistake, however, this is a commercial enterprise: the trailer bowed online as ticketing for the first screenings in December went on sale.

And it included glimpses not just of familiar faces such as Rey, Kylo Ren and Finn, but a handful of new, colourful aliens who will no doubt populate the action figure playsets and LEGO kits that will will this year's Christmas stockings.

They include a noisy new co-pilot for the Millennium Falcon, seen in a scene with the ship's much-loved first mate Chewbacca. And a white dog-like alien with what appears to be crystalline fur in a sequence outside the rebel base.

Among the trailer's key moments were sequences revealing a new design for the iconic AT-AT "walker", first seen in 1980's The Empire Strikes Back, and a confrontation between the new trilogy's heroine, Rey (Daisy Ridley), and its sinister villain, Supreme Leader Snoke (Andy Serkis).

"When I found you, I saw war, untamed power and and beyond that, something truly special," Snoke says in one of the sequences.

That confrontation may be intentionally reminiscent of the encounter between Luke Skywalker and Emperor Palpatine, which concluded the original trilogy of films.

Though the story of Star Wars is ostensibly about the rise and fall of the Empire and the rebellion against it, on a more thematic level it has always been a story of fathers, sons and inescapable destiny, notably Anakin Skywalker, his son Luke Skywalker, and from Luke a possible next generation of Jedi.

Much of the trailer's action is focused on the ancient Jedi temple on Ahch-To where - in the final scenes of the last film - Rey delivered to Luke Skywalker the lightsaber that was cut from his hand in a duel with his father, Darth Vader.

"Something inside me has always been there," Rey says ominously.

"I've seen this raw strength once before," Luke tells her. "It didn't scare me enough then. It does now."

Some of the film's key artwork and its over-use of red shadow around Luke Skywalker has fuelled speculation that Luke himself may "fall" to the "dark side" of the Force in the film.

Within the Star Wars canon, the "Force" is a mystical energy force which binds the galaxy together; those trained to use its power were known as Jedi knights, and they can manipulate it's light (good) and dark (evil) sides.

In past Star Wars films, the colour blue has been used to represent the light side of the force, and red its opposite "dark" side.

The film also includes a sequence which suggests that Kylo Ren (Adam Driver) is at the controls of a starfighter which fires a lethal shot at the Resistance command ship led by his mother, General Leia.

That sequence in the trailer, however, may have been edited for such a specific implication.

Ren - real name Ben Solo - is the son of General Leia and the late Han Solo.

What is known is that the character of General Leia will be killed off in the film; actress Carrie Fisher died earlier this year.

The trailer ends with Rey in a scene with Kylo Ren in which she asks him to "show me my place in all of this", to which he offers her his outstretched hand.

On the internet, theories are already abound that it is a sign she too will be seduced by the dark side of the Force, or the opposite, that in fact she will bring Kylo back to the "light" side of the Force.

Whatever it means, it is likely to translate to bums on seats come December 15 this year when "episode eight" - Star Wars: The Last Jedi - is released. The ninth and final chapter in the Star Wars "saga" will be released in December, 2019.