Valve may be secretly working on a new video game. In the most recent update of the Source 2 engine on GitHub, a user has managed to find new strings that could potentially imply on a completely new project. This may be connected to an upcoming video game or a mode in the already existing games in property of Valve.
Codename “Citadel,” this may be Valve’s current secret. Upon digging deeper, the YouTuber Tyler McVicker tried but couldn’t discover what precisely the codename points to, and as such, it is still considered to be a speculation.
We do believe that the Citadel may refer to a game mode in Dota 2. Citadel, being a Source 2 Project with a Top-Down view, implies on a Dota 2 alteration. But, more about that to be discovered soon.
You can check the video in which the YouTuber explains what else could potentially come under codename Citadel.