Petroglyph has released a new expansion for Grey Goo as a free update on PC, called Descent of the Shroud.

The Descent of the Shroud expansion features a new, fully designed faction that is playable in both multiplayer and offline skirmish mode against an AI-controlled enemy. The expansion also includes a single-player campaign mission that takes place after the events of the main story as it introduces and sets the stage for war against the Shroud.

The expansion also introduces new units to the game’s three original races. Betas can now deploy the Squall, which is a ranged ground unit capable of performing a knockback effect. The Goo Siphon is able to drain health from enemy units, which it can then transfer to allies. And the Humans’ Valiant AI bot is able to deploy a shield that redirects damage away from allies towards itself.

In addition to today’s free update, Grey Goo has relaunched as the Grey Goo Definitive Edition and now retails for $29.99. The Definitive Edition includes the original game, and all previously-released DLC and the complete soundtrack.