Hey there @lsugg3 - I sincerely apologise that your reply to this thread was missed previously, and that you did not receive a response until now.
I hope that since completing the opening sequences of Assassin's Creed Valhalla, you were able to access the settings menu and adjust your brightness / contrast to how you like it - but if not, and you are still having any issues with this at the present time, could you please confirm the platform you are playing on, and if you have performed any troubleshooting steps to try and address the issue? If on PC, can you please specify your system specifications and the type of display device you are using (i.e. a monitor or TV, and what brand / model).
Thank you very much!