In it, Lawless will reprise her role as the scheming Lucretia, with John Hannah returning as her husband, Batiatus, providing a back story to last year's surprise hit, Spartacus: Blood and Sand.
The prequel was dreamed up at the last minute, as a way to bide time after Spartacus himself - actor Andy Whitfield - was diagnosed with non-Hodgkin's lymphoma. A storyline that paused to focus on the house of Batiatus and its gladiator school before Spartacus arrived would give Whitfield time to undergo treatment and recovery before returning to the series and its demanding fight scenes.
But then there was more bad news. Whitfield's cancer returned, and he decided to bow out of the series to focus on his health.
"It was disheartening, not only because we had a lot of expectations and were gearing up for season two but because of how hard Andy was working," said Carmi Zlotnik, who oversees programming for Starz Entertainment and production of Starz' original series.
Steven S. DeKnight, the series' creator and executive producer, said he wasn't sure that the series could go on without Whitfield. A retelling of the 1960 historical movie starring Kirk Douglas, Spartacus: Blood and Sand shocked audiences with its explicit sex and nudity, highly stylised fight scenes and over-the-top blood and gore.
But Whitfield elevated the series with his moving performance as a man who is kidnapped by Roman soldiers and made to fight, driven by the promise that if he succeeds, he will be reunited with his wife, who was also taken into captivity.
And it was Whitfield who insisted that the production move forward.
In a statement to the Los Angeles Times, Whitfield said: "I had feared that the story would not be completed, and I am awed by Starz' commitment and courage to seeing this story through to its conclusion despite some extraordinary circumstances."
Last week, Starz announced that a new actor will step into the role of Spartacus when season two is expected to begin in January 2012: Australian Liam McIntyre.
DeKnight said that the writers brainstormed all sorts of ways to account for the change in Spartacus between the end of season one - when Spartacus leads the bloody revolt - and the beginning of Season two. Could Spartacus suffer a fatal injury in the revolt and a new Spartacus carry on his name? What if Spartacus had suffered some sort of facial injury, and the new actor carried that scar?
"But there's just no way to disfigure Spartacus that much," DeKnight said.
In the end, he said, the team decided that audiences were savvy enough to appreciate the gravity of what happened to Whitfield and the desire to move on with the storyline without resorting to trickery. McIntyre will simply assume the role when shooting begins in a few months.
The prequel grew out of a flashback sequence that was originally going to occur early on in season two to flesh out some of the characters, exploring Batiatus' gladiatorial school. It also sees the rise of a new gladiator, the cocky Gannicus. And there will be much more of Lucretia.
"It's true, you're going to see a lot more of Lucretia, but not just nakedness," Lawless said.
"People are going to be surprised by the relationship between Lucretia and Batiatus... Every decision she makes is out of her love and duty to Batiatus."
She said that while the prequel may have been born out of a need to kill time, no time is wasted.
"There is no foot-dragging in this prequel. We really go at it full-tilt," she said.
• Spartacus: Gods Of The Arena, starts on The Box on Sunday.
