Petroglyph is offering Descent of the Shroud, a new free DLC campaign for Grey Goo adding a new faction to the RTS game. They have also relaunched the Grey Goo Definitive Edition with the new content and a permanent price reduction. All the details can be found on the Grey Goo website, and you can get a look at the new content in this trailer. Here's word:

Grey Box, Six Foot, and developer Petroglyph have released a new expansion for Grey Goo®, now available as a free update on PC. “Descent of the Shroud” evolves the competitive, sci-fi, real-time strategy (RTS) game with a new, fully designed faction, playable in both multiplayer and offline skirmish mode against the AI. A new single-player campaign mission, taking place after the events of the main story, introduces and sets the stage for war against the Shroud, an enigmatic species that grows its units and structures, one which now threatens all life on Ecosystem 9.

“Descent of the Shroud” also brings new units to the game’s three original races. Betas can now deploy the Squall, a ranged ground unit with a knockback effect. The Goo Siphon drains health from enemies and transfers it to allies. And the Humans’ Valiant AI bot can deploy a shield that redirects damage away from friendly allies toward itself.

In addition, Grey Goo has relaunched as the Grey Goo Definitive Edition. This updated title, on Steam now for the permanently reduced price of $29.99, includes the original game, the previously released DLC campaign – “Emergence,” the “Descent of the Shroud” DLC, and Grey Goo’s expanded, complete soundtrack.

Grey Goo unites the best elements of classic RTS design with modern gameplay and production enhancements. Emphasizing tactical base-building and unit management, the game now features four distinct factions, each with their own units, structures and tech trees, across a sprawling single-player campaign and four-player local (LAN) and online multiplayer. Grey Goo has been actively supported since launch with DLC, free maps, terrain editor upgrades, a spectator mode, replay mode and dedicated multiplayer servers.