There appears to be no end to fan theories and speculations regarding the mysteries behind the leading characters of Star Wars: The Last Jedi, and they are unlikely to stop until the film releases worldwide in December.

Now, it looks like Mark Hamill is adding fuel to conspiracy theories by dropping hints about Luke Skywalker. On Wednesday, 1 November, he shared the international poster for Star Wars Episode VIII on Twitter and addressed rumours surrounding his iconic character. However, instead of clearing the air about Luke's future in the show, Hamill added to the confusion.

"Hey you Dark Side theorists: Look who's looming at the back of the poster now! Another clue for you all," he wrote. Post the Force Awakens, fans assumed that the former Jedi Master will follow in his father Darth Vader's footsteps and turn towards the dark side.

The initial poster for The Last Jedi with Luke in the background wearing his oversized robe almost confirmed the theory. Taking a cue from it, Hamill teased his fans by sharing the latest poster with Daisy Ridley's Rey in the background.

The latest poster is a stark contrast from the previous one as it shows Luke wielding his father Anakin's lightsaber. "Maybe it's now trying to tell us both luke and Rey is evil," one fan speculated. "Everybody is on the Dark Side! We know being a bad guy is way cooler anyway," added another.

In episode VII, Rey finally finds Luke, who has been living on a lonely planet in self-imposed exile after his nephew Ben Solo turns towards the dark side while training as a Jedi under him.

The space scavenger turned Force bearer handed over the lightsaber to Hamill's character at the end of the seventh sequel and it is assumed that Rey will be trained under him to control her powers, which is presumably more fearsome than that of Kylo Ren's.

At one point in the trailer, Kylo appears uncertain about his true self Ben and his evil alter-ego. Much like Kylo, Rey also appears to be struggling emotionally with her raw power. "I need someone to show me my place in all these," she tells Kylo who stretches his hand towards her in the previous promo.

Disney and Lucasfilm have masterfully crafted the promotional campaign for the eight instalments of the high-grossing franchise and considering the fan frenzy (despite major leaks) their efforts seem to be paying off.

Thanks to Hamill's latest tweet, Star Wars fans appear to be extremely excited as the debate about the dark side continues. Written and directed by Rian Johnson, the film also stars Carrie Fisher, Adam Driver, John Boyega, Oscar Isaac, Lupita Nyong'o, Andy Serkis, Domhnall Gleeson, Anthony Daniels, Gwendoline Christie, Kelly Marie Tran, Laura Dern and Benicio Del Toro.

Star Wars: The Last Jedi opens in UK theatres on 14 December, 2017 and on 15 December in the US.