Got a wild idea that masks are pretty much part of any culture, slavic and germanic included.
Since writing this post I got another idea about same thing, I'll post both.
#1 original idea:
A mask crafted from bones and block of woods and a pigment (defines subcolor of mask), giving +PSY +Stealth (x0.5), - CHA (+PSY * scent Q). During the night or in a cave / building, mask provides a small white radius of light (visible only for the mask user). If player wearing a mask commit a crime, the light that mask gives changes into the color of the biggest commited crime, enchancing radius of light (bigger crime, bigger light radius), that anyone can see. If the mask user commited a crime other than trespassing, (rummaging not included), He gets a debuff called "Curse of the Mask..." with prevents them from taking off the mask. KO, thief are disabled for the mask. Secondly, if someone's knocked out, someone else can freely equip them with a mask giving similer effect as above. It doesn't count as thief if that person wear a helmet. (special action against other player to prevent exploits?)
#2 idea while writing this post:
Make several types of masks that could be used instead of something. Example: make a farm mask made out off yellow pigment, straw and blocks, that enchances farming instead of the straw hat and several more masks just as to leave player with bigger pool of options to wear. (simple idea) Pagans had literally a mask for each occasion.
Or just combine both together, because, why not?