Contrary to rumors circulating in 2021-2022, is not a 60 FPS patch for consoles (that arrived separately via a compatibility patch for PS5/Xbox Series X). Instead, version 1.5.6 is a maintenance and compatibility update designed to:
Assassin's Creed Odyssey Update 1.5.6: Patch Notes and New Content Guide assassin+39s+creed+odyssey+update+156+download+patched
The core of the 1.5.6 download focused on squashing persistent insects that had plagued the title. Contrary to rumors circulating in 2021-2022, is not