Shikigami (式神 or 識神*)?, also known as shiki (式鬼*)?, is any demon or spirit summoned by onmyoji, the Japanese sorcerers, to follow their bidding. They are normally invisible, but can be bound to carefully crafted paper dolls to give them form. They can also possess animals and people in order to manipulate them. A shikigami with a weak master may go out of control, gaining its own will and possibly killing them.
"A common demon often used by Japanese sorcerers called onmyoji. They are used for many things, from common household chores to cursing others."
—Shin Megami Tensei III: Nocturne profile
Shikigami often roam the Shinjuku Medical Center's halls. At level 4, they can be recruited by the Demi-fiend for a useful addition in defeating Forneus. Shikigami will also appear in Shibuya and Ginza.
Shin Megami Tensei IMAGINE
"A type of demon gods used since ancient times in Japanese divination. There are many different types of Shikigami, some taking the form of paper, others of elements, and still others of various monsters and demons. They cannot be seen by ordinary people, and possess the ability to change themselves into many shapes. The famous diviner Abe-no-Seimei commanded the so-called Twelve Divine Generals, the most powerful of all Shikigami. Besides carrying out secret missions for Seimei, these Shikigami also performed various everyday tasks for him. The Shikigami commanded in the Izanagi school of divination practiced in Kochi on the island of Shikoku is called Shiki-Oji, and is said to be extremely powerful."
—Shin Megami Tensei IMAGINE compendium
Shikigami appear as an early boss in act 3 of the main story and become reoccurring mobs in the later acts. They also are one of the two summons the four oni bosses of Shinjuku field can summon for support.
Persona 2: Eternal Punishment
Four Shikigami accompany Chizuru Ishigami during a confrontation in Sumaru TV. All of them look identical, but have different weaknesses. The trick to tell them apart is their battle quotes, which differ from each other.
Devil Survivor 2: Record Breaker
Shikigami are servants of Shiki-Ouji, with two joining each Shiki-Ouji in battle. Sacrificing one will revive a fallen Shiki-Ouji and its two Shikigami. Hence, to defeat Shiki-Ouji safely, each individual Shikigami flanking each Shiki-Ouji clone must be defeated before the clones can be taken down.