What does the shull on Minnies fighting and regular clothing along with her school uniform represent? Does it assist her with her powers या something? या is it an accesory?

the skull was a gift दिया द्वारा grim to minnie and is worn like a brooch, it closely resembles grims actual skull and i think it was दिया to symbolize that she is his child and he wants her to have something that represents him. i dont think it has powers but it can change facial expression like its alive

Grim gave it to Minnie as a gift. And since it resembles Grim and Grim is her father ( -cough- kinda -cough- )she wears it all the time