User with this ability either is or can transform into a personal demon, a being within a person's mind that personifies a specific event or trauma that person has experienced. Their existence is often to blame for whatever mental or emotional problems the person has. It is possible for them to manifest in the real world as hallucinations.
Kochamara (Psychonauts) is a mental broadcast from Oleander into Linda's mind as a means to control the monstrous lungfish.
Jasper Rolls (Psychonauts), also known as "The Phantom", is the source of Gloria's psychosis.
Napolean Bonaparte (Psychonauts) is a genetic memory responsible for Fred Bonaparte's psychosis.
Dingo Inflagrante (Psychonauts), based after the varsity cheerleader that stole his girlfriend, is one of the sources of Edgar's psychosis.
Lampita Pasionado (Psychonauts), based off of his high school girlfriend, is one of the sources of Edgar's psychosis.
Augustus Aquato (Psychonauts), because of the way he treats Razputin, manifests from his son's mind as a being who tries to kill him.
The Keeper (The Evil Within) is a manifestation of Ruben "Ruvik" Victoriano's rage at the theft of his files from his personal safe by Dr. Marcelo Jimenez, made real in the STEM mental-scape.
In order to keep Juli set on her mission, MOBIUS injected her with a serum that manifests in her mind as the Administrator (The Evil Within: The Assignment) a black, shadow-like entity that haunts her throughout her mission.
The Queen of Hearts (American McGee's Alice) is the manifestation of Alice's madness, made into her monstrous form after the death of Alice's family in the fire.
Dollmaker (Alice: Madness Returns) is the manifestation of Dr. Angus Bumby's influence on Alice and is the source of Alice's returning madness.
The Corrupting Blood (Castlevania Lords of Shadow 2) is the manifestation of the lonely castles haunting revenant that manifested the attributes of Gabriel's maddening bile and venomous hatred towards god in physical form, taking shape as Inner Dracula turning the castle itself against him to become whole with it's counterpart once again.
The Beast of Darkness (Berserk) is the manifestation of all of the rage and hatred in Guts's soul as a result of the hellish ordeal of the Eclipse, and his feelings of vengeance against Griffith and the God Hand for what they have done to him. The Beast wants Guts to throw his humanity away and become a monster like those he fights.