Natural Selection 2: Combat is a first-person team-oriented multiplayer shooter developed by Faultline Games and published by Unknown Worlds Entertainment. Players fight for either the Trans-System Federations (TSF) Space Marines or the Alien species known as the “Kharaa”, with both sides having a completely different set of lifeforms and abilities. The marines rely heavily on an array of high-tech ranged weaponry and mechanised armor, while the aliens rely on stealth, speed and strength. Additionally, aliens can evolve from a small but nimble and dangerous creature into one of five life-forms with unique abilities. NS2: Combat features intense two asymmetric teams in a fast-paced fight for survival, implemented using the beautiful Spark engine.

You can read more directly from the developers website

There is a 96-hour mega-stream for NS2 Combat at the Fault Line Games Twitch.tv page