Many players on the PC version of Assassin's Creed Valhalla have found a way to access premium cosmetic items for free. This method is thanks to the modding scene, and you can check out this video on Nexus Mods for a more detailed look at how it works.
The method involves using a program like Cheat Engine, a free memory-scanning software, to view and inject directly into the game's memory, allowing you to change certain aspects of the game. In this case, it is the ability to obtain premium cosmetic items that would otherwise only be obtainable from purchasing with Helix (Valhalla's premium currency).
As reported by Eurogamer, many have even taken it a step further to mod in and obtain cosmetic items that are not currently available in-game.
These premium cosmetic sets cost around 2000 Helix at standard prices, which will run you about $20. Using this method, many have circumvented the need to spend additional money on the game.