During that month, specifically on December 28th, a Horizon Forbidden West game file called "TestGame" was leaked, but after a while we realized it wasn't a new game or anything like that. In fact, it was an alpha leak for the game.
An alpha build contains the game with its bugs and a complete list of bugs, but fortunately, this build is completely locked and unusable. We've seen these types of leaks a lot in recent years, but if we look closely, we'll see that these games are from the previous generation and previous generations, but Horizon Forbidden West is the first current-gen game to receive this type of leak.
This post was shared on Reddit, and the publisher even made the entire build available for sharing. The Decima Engine (Horizon Forbidden West's game engine) appears to have some great technology that has made the alpha build easily accessible to the most skilled developers and made the game fully open-source.
A complete, non-public internal build of Horizon Forbidden West with the full Decima engine build enabled for debugging has been publicly leaked. from GamingLeaksAndRumours
The leak is a major blow to the developer. It will allow users to walk through this build and get a glimpse into the inner workings of Horizon Forbidden West. This build may allow users to reverse engineer it and create an unofficial version for PC platforms.
Notably, as fans of the series have come to expect, the co-op title Horizon appears to be in development and remains an open-world game, with a continued focus on narrative. According to the lead writer's job description: "Our writers are driven to push the boundaries of dramatic storytelling in open-world games. We want players to feel hooked on our quests and characters, enjoy the constant dialogue, and enjoy our stories for a long time." We look forward to seeing more from this unique project.