Magic, Spirits, and Mysteries
Maisu are demons from the Bitter Barrens. They are creatures of spite, fuelled by wickedness and ill tempers.
Objects can be possessed by maisu, and when that happens, it corrupts the object in question. Demons in general prefer possessing objects that have movable joints, such as dolls, foldable furniture, or – in very rare cases – Elden machinery. Possessed machinery often tries to hide its possession and continues to work as normal, but the result of its work tends to show proof of it.
Maisu are demons, not folk, but they are capable of complicated emotions nonetheless, such as regret and remorse. While they are not able to possess people or animals, they can inflict sickness, and physically harm them.
Summoning a maisu is mostly done intentionally, but tales suggest that there have been instances when they also appear spontaneously. If that is the case, no scholar has been able to determine how or why. Demon summoning is no easy feat, and many failed would-be summoners have sown the rumour that perhaps maisu do not exist at all.