According to the writings in The Lesser Key of Solomon, Forneus is the thirtieth demonic spirit listed in the Ars Goetia. He is a Great Marquis of Hell with twenty-nine legions under his command, partly comprised of the order of angels and thrones, and appears as a sea monster. When summoned, he can make men well-versed in rhetoric, give them a good name, teach them foreign tongues, and make them trusted by friend and foe alike.
His name seems to come from "fornus" (oven). He can take many different forms but mainly prefers his human form.
"Origin: Israel. One of the 72 demons of the Goetia. He was one of the Thrones who fell from grace. He appears as a silver sea monster, but can take the form of a human as well. He grants knowledge of various arts and sciences to hims summoner. He can also change the hatred of one's enemies to something like friendship."
—Shin Megami Tensei A-Mode DDS dictionary
Shin Megami Tensei III: Nocturne[]
"One of the 72 demons of the Goetia. He appears as a great sea monster. He is skilled in languages and is a master of rhetoric."
—Shin Megami Tensei III: Nocturne compendium
Forneus is the first boss, fought in the Hospital when the Demi-fiend reaches the exit. A Decarabia in Shibuya claims to be Forneus' friend and is annoyed by the latter's supposed tardiness, although there is no given explanation for their friendship.
Shin Megami Tensei: Strange Journey Redux[]
Forneus is the boss of the Fourth Sphere of the Womb of Grief. He swears to avenge Amon by fighting Alex, but chooses to settle with the protagonist when he makes it to Forneus before she can.
Forneus' attacks are mainly physical and ice-based. His signature Death's Bite hits random targets 4 times, and he telegraphs this by using Charge. Once he hits half health, he unleashes Abyssal Prison, which is a field effect that lets him auto-cast Abyssal Scream at the end of every turn for 3 turns, inflicting Fear across the party.
Despite all this, he shouldn't be so tough. At this point, if one has been diligent with gathering D-Sources, Luster Candy and Debilitate should be easily acquired. His weakness to Gun Skills makes it easy for the protagonist to constantly exploit his weakness. Fight conservatively, though, as the protagonist gets into another boss fight immediately afterwards.
After his defeat, Forneus surrenders the Fourth Fruit. He also becomes available for fusion and unlocks the way forward. Forneus' fusion requires Decarabia, Kikuri-Hime and Sui-Ki. He leaves behind the Spotted Leather forma, which is used to create the Sub-App Co-Op Enhance C, which allows Co-Op attacks to trigger on critical hits.
Shortly after he retreats, though, Alex appears and attacks the protagonist.
Shin Megami Tensei IMAGINE[]
Forneus appears regularly in the early story missions as a boss and as support for demons such as Eligor in his boss instance.
Shin Megami Tensei V[]
"One of the 72 demons of the Goetia. He appears as a great sea monster and is skilled in many languages in addition to being a master of rhetoric."
—Shin Megami Tensei V lore
Devil Summoner: Soul Hackers[]
Forneus appears in the 3DS remake as a demon unlocked in Nemechi's cat form and can be purchased for 100 D-Souls. He is the earliest demon available with access to Makakaja.
Persona 3[]
"One of the Goetia's 72 Demons, he appears as a great sea monster. He is linguistically skilled, and a master of rhetoric."
—Persona 3 background
Forneus can be obtained via fusion, or through Shuffle Time in the second block of Tartarus, Arqa. The special non-mythological relationship with Decarabia is rendered again in this game, in which these two Personas are able to perform a combo skill called Best Friends.
Reload[]
"One of the 72 demons of the Goetia, he appears as a great sea monster. Known as the great Marquis of Hell, he is skilled linguistically, and is a master of rhetoric."
—Persona 3 Reload background
Forneus is a Persona of the Emperor Arcana. He is one of the material Personas used in the fusion recipe of Flauros.
Persona 5[]
"One of the 72 demons of the Goetia, he appears as a great sea monster. Known as the great Marquis of Hell, he is skilled linguistically, and is a master of rhetoric."
Forneus is now the ninth Persona of the Magician Arcana and can no longer learn Marin Karin by leveling up, learning Brain Jack instead. When itemized with an Electric Chair, Forneus now yields the Psiodyne Skill Card. During a fusion alarm, Forneus will yield the Mapsiodyne Skill Card instead.
In the Path of Da'at, the shadow has an unrecruitable super variation called the "Omniscient Fish of the Sea" who is accompanied by a Shadowless Pentagram.
Digital Devil Saga: Avatar Tuner[]
Forneus will appear after defeating lone Isoras in the northern tunnels of the Samsara Tunnels.
Shin Megami Tensei: Liberation Dx2[]
"One of the 72 demons of the Goetia. When summoned it appears as a large winged fish or similar sea creature. This creature is especially well veersed, teaching its summoner the art of rhetoric. One who masters Foreus' craft is able to convince even the most stubborn minds."
Requests Macca. After using on the same clan of demons thrice, any demon of that clan will take away one third of player's Macca forcefully in the next encounter.
Kazuma Kaneko made his design look like a manta ray because the manta ray are sometimes known as "devil fish." In Japanese, the type of ray/batoid bears the connotation of devil is the giant oceanic manta ray (鬼糸巻頴娃, oni ido maki ei)?; Forneus appears as a sea monster. The demon's skeletal structure, namely its spine and forelimbs, also bear a distinct resemblance to a human body.
The non-playable Decarabia in Shibuya in Shin Megami Tensei III: Nocturne waits for Forneus, unaware that he was already defeated. He's waiting next to the Statue of Hachiko, indicating it's a reference to the real life shiba inu dog who waited for his owner next to the station unaware of the fact that his owner died at work.
In the Path of Da'at area of Mementos in Persona 5 Royal, Forneus and Decarabia can be encountered together, as another reference to their special non-mythological relationship.[1]