For the average player, this is just an old update. For the digital archaeologist, it is a treasure trove of cut content, unused voice lines, and a glimpse into Playground Games' internal naming conventions (Rune -> Hidden Horizons -> maybe an actual Mythology expansion?).
Published by: Horizon Garage Reports Date: October 26, 2023 (Editor’s Note: This article covers a specific archival build often referred to by the community as the “Rune” precursor) forzahorizon5updatev1671650runepart1
If you have stumbled across this file name in your Steam download queue, a community forum, or a modding repository, you might be wondering: What is the "Rune" update? Why "Part 1"? For the average player, this is just an old update