Long short story, after spending a good 2 hours making my Custom Mask mod, I encountered this issue. The Mask itself looks good, but for some reason, it hides all facial features (Hair, eyes and mouth). I couldn't find a solution to this. Notes: I used a template from armors\decorative\hats The image background was left unchanged (transparent) Configuration file is fine, mod works properly. I've used Paint.net to remove the previous hat and add mine over it (this was to have an idea of where the player head is.
the file below is for items\armors\other\wildfungus (the file seems purely white bc that is the only color in the file, but there are some transparent areas) where the mask file is white is left unchanged while all player pixels in the transparent section is made transparent. if you do not have this file, idk what exactly would happen, but i do know with this file completely transparent everything connected to the head is removed