Okay, let me clarify. It's not actually Darth Maul, and it's not the guy who played Darth Maul in Episode 1, it's the guy who did the voice for the guy who played Darth Maul in Episode 1. So a few degrees of separation there. But still! Darth Maul is in Dark Souls II. Awesome.
The actor in question is Peter Serafinowicz, and he did the brooding baritone voice over for Darth Maul. He plays a character called Mild-mannered Pate, a mysterious treasure hunter. But let's face facts — everyone in the Dark Souls universe is mysterious. That's a series that's plenty sparse with its lore.
Peter has also appeared in comedies like Shaun of the Dead, Parks and Recreation and South Park. You can check out some of his performance in the above video.
To be honest I just wish the game would hurry up and come out already.