
Among them are creatures in human or animal form, specters, monsters, personified natural phenomena, gods that have lost their divine condition, objects with spirit, etc.
It is important to note that what we understand by "ghost or disembodied soul" is not considered yokai.
Not all of them are evil and violent. Many of them bring fortune, help people or play with children.

Hyakki Yakō (Night parade of the hundred demons). Fragment of a scroll painting by Hitaya Keii Hironaga, 1800(c.)