We are adding a really, really awesome unit with an 'interesting' title to it. And you have to play a certain way to unlock it. It just isn't going to happen by accident; it's a combination of things you'll have to do. I know I'm being vague about it, but it's probably the most awesome unit in the game. You're not going to find it in the Civilopedia or the unit list, you're just going to find out that you can build it during one session