Goetia, possessing Solomon's living body, takes on the role of Grand Caster (グランドキャスター, Gurando Kyasutā?) for much of the story of Part 1.
Profile
After King Solomon’s death, the 72 demons that were sealed away inside his corpse awakened to their own ideology, swindled Solomon’s name (although, from their point of view, they are the true King of Magecraft Solomon) and embarked on a new venture to convert the entire mankind into energy. And thus, Goetia resumed activity by making King Solomon’s corpse into his nest, but there was a great dilemma in his way of being.
Appearance
Ten rings have been inserted on the fingers of his two hands, but that on the middle finger of his left hand alone is a replica.
Personality
Since he has King Solomon as a base, his personality is intellectual (albeit frightening). That being said, as he is the aggregate-body of the 72 demons, his personality・disposition amounts to 72. Because he is an individual and a colonyWP, whenever talking to others, a “demon” resembling the other party comes to surface. This is the reason why Goetia’s disposition is evaluated as that of a “mirror”.
He possesses an almightiness that causes the entire logic of the universe to obey him, and a sense of intimidation that seems to say that he hates all of mankind. Originally, he would have more than enough qualifications as a king that rules over men. However, he could not understand humans due being almighty, could not achieve an answer due being immortal, and thus was unable to become “a human king”.
Role
Fate/Grand Order
After Solomon's death, the 72 Demon Gods, who were much like shadows of Solomon, were left behind to protect Human Order. Over time, the Demon Gods aggregated inside Solomon's corpse to form Goetia, Beast I.
Goetia posed as the enterprise of the one who called himself King of Magecraft Solomon began. He built Holy Grails as Singularities that distorted history, embedded on human history magi that he designed (to transform into demons according to Goetia’s will) as offsprings and produced seven detonation points. That is the cause behind the collapse of the cornerstones of anthropic principle in each eras. When said scheme was concluded, mankind lost the future beyond 2016.
London: The Death World in the City of Demonic Fog
"Solomon" appears as the final antagonist and the one behind the whole Singularity, who Makiri Zolgen, Charles Babbage and Paracelsus serve. After the defeat of Nikola Tesla and Artoria Alter, Solomon appears and faces Ritsuka Fujimaru's party with four Demon Gods, eliminating Shakespeare, Kintoki and Tamamo no Mae. Solomon nearly kills Mordred, but she is saved by Andersen, who confronts Solomon about the origin of the Holy Grail War system. Solomon confirms Andersen's theories, revealing himself to be Grand Caster, killing Andersen afterward. Solomon then decides to withdraw, as he doesn't see Chaldea as a real threat until they destroy the seven Singularities.
Babylonia: The Absolute Frontline in the War Against the Demonic Beasts
Salomon: The Grand Time Temple
During Chaldea's skirmish on the Time Temple, Solomon is implored by Baal to activate Ars Almadel Salomonis to eliminate the Heroic Spirits. However, Solomon counters that more will only come, and states that only Ritsuka, the Heroic Spirits' only connection to the Singularity, needs to die to remove them.
Later, Solomon is confronted by Ritsuka Fujimaru and Mash Kyrielight, to whom he explains both his Noble Phantasms and his plan to use the Magical Energy from humanity's destruction to power his true goal. He then goes to kill Ritsuka in order to remove the Heroic Spirits, but he is blocked by Mash.
Abilities
His Class was determined by his achievements. Grand Caster and the likes are nothing but fake ranks. Created by humans, this is the great disaster that has most effectively misused human history.
Those who make eye contact with him will have their Soul removed from their body and sent to a Purgatory of Goetia's own creation. It is not as effective against Servants and other spiritual bodies, but his gaze still forces them to drown in their flaws and relive past mistakes.
Having nested inside the corpse of King Solomon for a long time, and being the aggregate form of the seventy-two Demon Gods, Goetia has access to all his Skills and Noble Phantasms. While inhabiting Solomon's body he possessed a Saint Graph identical to that of a Grand Caster, as such his energy output was so much greater than that of regular Servants that no matter their rank they pose no threat to him. Whereas servants are weapons meant to fight individuals he is a weapon meant to fight the world. Although Goetia commands supreme power as the King of Magecraft, Kingu claimed that even him wouldn't be able to stop Tiamat despite her not having fully awaken and being still restrained by the seals that had been placed on her.
Skills=
Territory Creation (Rank A): Creation of a "Workshop" territory that is advantageous to himself as a magus.
That ability of his that had created the Temple of Jerusalem is of the highest peak of Territory Creation.
High-Speed Incantation (Rank A): The ability to hasten magic incantation speed. Formerly his incantation speed is only average, but now it is comparable to High-Speed Divine Words. That is due to the inside being Goetia, and thus his weakness from when he was alive... his characteristic weakness... isn't there.
Item Construction (Rank C): Creation of tools tinged with magic energy. Perhaps because he is specialized in contracts, his Item Construction ability is on average level.
Summoning (Rank EX): A skill that Magecraft evokes spiritual bodies from the past, or possibly from the future. After the death of King Solomon, the concept of “72 demons” that he left behind nested inside the remains of King Solomon and was reborn after a long time as “someone” that put on the mask of King Solomon. Although he cannot perform Heroic Spirit summoning nor invoke normal Familiars, he can freely summon any of the 72 demons on the present age. Maybe it is easier to understand if described as a converter that projects the “fictional demons” nested within King Solomon’s inner world on the physical world.
Solomon's Rings (Rank EX): The ten rings given by God. The mark of the king, the progenitor of magic.
In the case of all ten rings present, any and all kinds of magic performed by mankind is invalidated and put under his subordination. There are 9 rings worn by Goetia. The remaining one is-----
Clairvoyance (Rank EX): Eyesight of good quality. Apprehension of long distance target and elevation of kinetic vision. When the rank is high enough, even x-ray vision or future prediction becomes possible.
Solomon's Clairvoyance gives him unobstructed view of both the past and the future. Due to Clairvoyance being a Skill embedded to the body, it can be used by Goetia.