In 20th Century Fox, Ubisoft Motion Pictures and Regency Pictures' upcoming adaptation of the Assassin's Creed video games, Michael Fassbender plays a Death Row convict who wakes up from his execution not in heaven or hell, but in a top-secret scientific facility run by the sinister Abstergo Industries. Now a "patient" instead of a prisoner (according to his captors, at least), Callum Lynch is forced to use a machine called the Animus to relive the memories of his ancestor - a 15th century Assassin called Aguilar de Nerha.

Cal isn't alone in Abstergo's facility however. The company - which is actually the modern front for the Templars, ancient enemies of the Assassins - has several other subjects who are all being used in the Animus experiments. During our visit to the set of Assassin's Creed, we saw a communal area where each of the subjects work on their own crafting projects - and easily the most eye-catching among them was an altar covered in voodoo dolls and mysterious herbal mixtures.

This is the work of Moussa, another involuntary guest at Abstergo, who is played by Michael K. Williams. Boasting an enviable list of TV and movie credits, Williams is perhaps best known for his roles as Omar in critically-acclaimed crime drama The Wire and Chalky White in HBO's Boardwalk Empire, and more recently he landed roles in action film Triple 9 and the upcoming Ghostbusters reboot. Though he admits that he's "not a gamer" and had never even heard of Assassin's Creed before being sought out for the role, Williams was extremely enthusiastic about his character(s) in the movie.

"My character, he’s in this prison, whatever this place we call it. His name is Moussa. He is going to… When he becomes an Assassin, he’s going to channel his ancestor, which is a voodoo poisoner who has been dead for about 200 years. His name is Baptiste."

The name and character will be familiar to hardcore fans of the games, as Baptiste is the second character from the video games confirmed to be in the movie - along with Jeremy Irons as Alan Rikkin. Baptiste (and there are far too many coincidental details for this not to be the same character) appears in Assassin's Creed: Liberation, a title originally released for the PlayStation Vita and later ported to consoles. Interestingly, Baptiste is an antagonist in that game: an Assassin who turns away from the Order and forms his own cult. Let's hope Moussa doesn't follow in his ancestor's footsteps and end up turning on Cal.

Assassin's Creed - Baptiste
Baptiste as he appears in the games

The first trailer for Assassin's Creed teased scenes of Abstergo's patients using the skills they have learned from their Assassin ancestors to try and break free of the facility - though whether this breakout attempt will succeed remains to be seen. What we do know is that Moussa will be Cal's main point of contact among the patients - his big brother, so to speak.

"That’s pretty much where we’re at right now with it, just all of us finding each other, learning to trust each other, and getting out of this hellhole that they have us imprisoned in so that we can become who we were destined to be... Moussa is what we call the trickster. His whole thing when Cal comes into the prison, he sees him as the missing link to the puzzle and immediately realizes that we need to bring him into the fold, the family, and to make him feel safe in this room full of crazies. So that’s Moussa’s relationship to Cal right now, is to bring him into the family, make him feel comfortable, and to let him know that we all need to get out of here. "

When asked about his historical costume, Williams admitted "I haven't seen it yet" (this was about halfway through the movie's production), but confirmed that audiences will get to meet Baptiste. "I just hope he looks like a badass, basically," Williams said, when asked what he hoped his costume will look like. "I just really want him to look non-traditional. He’s a voodoo assassin. Whatever that means. I just don’t want him to look typically like anything. Just Baptiste."

Assassin's Creed - Abstergo breakout

The little voodoo altar in the crafting area is, according to Williams, where Moussa keeps his "weapons." It might seem like a bad idea for Abstergo to be handing weapons to their captive Assassin descendants (in the trailer, Cal is shown being equipped with his ancestor's wrist blades), but Williams says that Abstergo actually encourages their patients to learn how to be dangerous.

"Even in this place, there’s not a secret that we have powers. So they know that Moussa plays with magic and things of that nature. And they encourage that we do these things so they can siphon it out of our brains with the thing they stick in the back of our heads. They want our power on some level. So they give us the little safe havens of, they feel, safe environments to play with our gifts."

Of course, Moussa's killing skills aren't all voodoo and poison. "He definitely has some assassin skills," Williams says. "He prefers to use trickery and magic and voodoo to slay his opponents as opposed to just hand-to-hand combat. But... he could take it to the mat if he had to." It sounds like Abstergo may have bitten off more than they can chew when it comes to this Assassin and his ancestral skills.

NEXT: Michael Fassbender Explains the Animus Redesign

Assassin's Creed arrives in theaters on December 21st, 2016.