The spell can only work on people who suffer from a dissociative identity disorder, or because of madness or a strong imagination, they believe that a being that appears only in their mind really exists - like a child's imaginary friend.

The imaginary being  leaves your body and enters the container you used for the spell's material component. Imaginary being becomes ethereal, but cannot see in the ethereal plane. It can take actions up to 100 feet out of the container or attempt to possess a humanoids body. Its etheric body passes through objects and surfaces but has the ability to cast spells that do not require touch or components if it is unable to use them.

Imaginary being can attempt to possess any humanoid within 100 feet of container that it can see (creatures warded by a protection from evil and good or magic circle spell can't be possessed). The target must make a Charisma saving throw. On a failure, imaginary being moves into the target's body. On a success, the target resists its efforts to possess it, and imaginary being can't attempt to possess it again for 24 hours. The target can make a Charisma saving throw at the end of each of its turns. On a success, the possess ends.

Once imaginary being possess a creature's body, it can control it. Imaginary beings game statistics are replaced by the statistics of the creature, though it retain your alignment and your Intelligence, Wisdom, and Charisma scores. Imaginary being retain the benefit of its own class features. If the target has any class levels, you can't use any of its class features.

While possessing a body, imaginary being can use its action to return from the host body to the container if it is within 100 feet of it. If the host body dies while imaginary being is in it, the creature dies, and you must make a Charisma saving throw against its own spellcasting DC. On a success, imaginary being return to the container if it is within 100 feet of it. Otherwise, imaginary being die.

If the container is destroyed or the spell ends, imaginary being immediately returns to oryginal body. If oryginal body is more than 100 feet away from imaginary being or if oryginal body is dead when imaginary being attempt to return to it, it dies. 

When the spell ends, the container is destroyed.