Mary is one of the last necromancers in the world. She is able to use dark mana and connected to death. Because of that she is considered evil by others, and so hides herself and her scars with her cloak. She is gentle and cares for others but is unable to show her emotions and is often compared to a robot. This tea is to demonstrate that there is a sweet interior covered by the darkness.
-From the world of Trash of the Count's Family