Mass Effect and Mass Effect 2 lead writer Drew Karpyshyn has left Bioware again.

Karpyshyn left the studio in 2012 to work on his Chaos Born trilogy of novels, but returned in 2015 to continue working on Star Wars: The Old Republic and Anthem.

He will now focus on freelance work, novels, and a graphic novel project.

He will also work with FoxNext Games' new Fogbank Entertainment studio on an episodic narrative game based on one of 20th Century Fox's franchises.

Notably, Fogbank studio director Daniel Erickson is a 17-year BioWare veteran, and the studio's writing director Alex Freed also did a stint at the Anthem developer.

"I know a lot of you are wondering why I’m doing this," Karpyshyn wrote on his website.

"For many people, working at BioWare would be their dream job and they can’t imagine anyone stepping away from it. But it was time for me to move on.

"Everyone who works at BioWare pours their heart and soul into the games they are making," he added.

"It’s creatively demanding and – at times – exhausting. In the past, I’ve managed to juggle outside projects with my work at BioWare, but it always took a toll. And there were always outside projects I had to pass on because they would represent a conflict of interest with BioWare or EA properties. So I made the decision to step back (again) and focus on my freelance work."