Rosenberg provides some info about the DLC and denies the rumor that this content was originally cut to avoid slipping the game.
Eurogamer: You've said that Lara's Shadow has a brand new playable character. Is the name as much of a giveaway as we expect?
Ron Rosenberg: Yes, there is a brand new playable character in Lara's Shadow, the Doppelganger. The Doppelganger is a dark and deadly double of Lara with incredible powers and instructions to end the Croft lineage once and for all.
I think people are going to have great fun playing the bad girl character of the Doppelganger. We're quite proud of how she turned out. The release is a great example of using DLC to innovate and try new ideas and I can't wait to hear what the fans think of it. We developed new gameplay mechanics to support her superhuman strength and agility that make the experience different than any other Tomb Raider game. It's a rush to play.
She also presented some quite intriguing storytelling opportunities for us. As the Doppelganger likes to boast, she is a copy of Lara "with the flaws removed", and getting to know her provides some insight into Ms Croft.