While reports of bans for single-player games like Valhalla are rare, there is always a non-zero risk of losing your entire Ubisoft account and all purchased games.
Most unlockers work by replacing or adding a .dll file (like uplay_r2_loader64.dll ) into the game’s main directory.
Using a DLC unlocker allows players to access paid content in a legally owned base game. For Assassin’s Creed Valhalla, this process specifically involves bypassing Ubisoft’s ownership checks. How DLC Unlockers Work for AC Valhalla
Разблокировка всех DLC в Assassin's Creed Valhalla - VK
This is the primary tool used for games released after 2020, including AC Valhalla. It "tricks" the Ubisoft launcher into believing your account owns the licenses for specific DLCs.