Atreus is the Deliverer of the Halloween-Spirit

Official Sentius Lore: Sentius are beings that are able to carry and deliver emotions and thoughts. They are able to make feelings materialize to form letters. They keep the letters within their body, through a letterbox slot located on their chests. As long as they are able to place the letters within them, it will be protected by them.

The letters themselves are a tangible physical matter, however, and can be held by anyone or anything. Each Sentius has their own seal which will appear as a wax seal on the letters they guard. The seal cannot be opened by anyone other than its corresponding Sentius or the intended receiver.

Sentius begin without emotions, but learn to feel from the emotions of others they carry within them. Thus, their personality is formed from said emotions. The emotions they deliver also influence the appearance of the tattoos on their body.