The user can create any creature (be it real or not and more than likely not) out of their imagination or mind, and be able to control it. The user can make the creature do their bidding and follow their commands. The user can also destroy the creature created once they are done with it.
Since the user's creation is imaginary it is technically not real and most likely invisible making it near impossible to attack it.
Mac (Foster's Home for Imaginary Friends)
Goo (Foster's Home for Imaginary Friends)
Madame Foster (Foster's Home for Imaginary Friends)