Goetia

"Everything will begin once more from Genesis, and a planet without the concept of "death" will be made. That is our great undertaking. We did not destroy mankind out of hatred."

- Goetia

"Numerous Demon Gods have burned to ashes. The Temple is destroyed, too. Following my own annilation, the Human Order Incineration Ritual shall be destroyed as well. However, I shall never give in until the battle has its victor. Start now, the Master from Chaledea. Your victory shall be burned down by my own hands."

- Goetia as the Human King, before his final battle against the Protagonist

Goetia, also known as King Solomon, Beast I and the Grand Caster, is the primary antagonist in the overall Fate/Grand Order: Observer on Timeless Temple.

Goetia is the First Beast from the Evils of Humanity, representing Pity (as in "the sheer arrogance of people pitying and being disappointed in other people"). He is the mastermind behind the seven Orders and the attacks on humanity. He's also the one behind the attacks on the Human Order.

He is voiced by Tomokazu Sugita, who also voiced every Demon Pillars and Professor Lev Lainur Flauros in the same game. While disguising as Solomon/Grand Caster, Goetia is co-voiced by both Tomokazu Sugita and Kenichi Suzumura, the latter also voiced Dr. Roman and the real Solomon in the same game.

Overview
"That's right! That's exactly right! Actually, you lot are even lower than piss! You mean nothing to me. Whether you live or die here is utterly inconsequential. Understand? I'm not overlooking you. You weren't worthy of my attention in the first place!"

- Goetia (as Solomon) showing disdain to Mordred in London

Goetia is the aggregate body of the 72 Ars Goetia demons invented as "a system to efficiently promote proper reason" by King Solomon. Said system had a will; it grieved and raged against the relationship between their master and humans, as they wished to conquer the human imperfections their creator always ignored. Eventually, they transformed into a curse that takes action to conquer "the imperfectness of humans" that King Solomon continued to ignore. It eventually changed into the Human Order Incineration Ritual (人理焼却式, Jinri Shōkyaku-shiki?). After Solomon's death, they were sealed away in his corpse and awakened to their own self. They took Solomon’s name, considering themselves to be the true King of Magecraft. They embarked on a plan to convert mankind into energy, attempting to reach the origin while making use of all human history, to create a world without death.

What he wanted was to make a perfect world without death for humanity, he just doesn't know the worth of mankind's mortality until the second boss fight with him as the Human King Goetia, where he asks you to remember him now that he will perish.

Goetia believes so righteously in his goal and convictions that he will never give up to see them through. When Roman destabilizes his existence with Ars Nova, Goetia still carries forward with his plan, knowing that he simply needs to hold off Ritsuka long enough to pin down the coordinates for his time reversal. Even after his first defeat, when his Demon Pillars are breaking away from him in droves and he's weakened to the point that a Command Spell-reinforced Ritsuka can finish him off, Goetia still refuses to stand down, only failing to execute his plan because his space-time coordinates had a small margin of error. Even then, Goetia refuses to die when he is killed, his residual consciousness possessing Solomon's rapidly decaying body for one last fight against Ritsuka.

Cosmos in the Lostbelt
While initially believed to be destroyed, Goetia appears as the off-screen narrator of the first Preview of Cosmos in the Lostbelt, pretending to be Solomon once more and narrating the coming storm towards Chaledea and humanity, as well as the rise of Lostbelts. However, he showed some anticipation towards the upcoming battle.

It is widely presumed that Goetia is still alive somewhere, since there was a mysterious fighter who was mentioned in both Russian Lostbelt and Nordic Lostbelt, helping the Chaledean Crew and Lostbelt citizens, but he never mentioned his name.

In Moonlight/Lostroom OVA, Goetia is mentioned by Galahad when he abandoned the Protagonist and Mash. Galahad blames the protagonist entirely for the current crisis of the Alien God and the Lostbelts, as Goetia's defeat directly caused the rise of the Crypters. Galahad makes it clear that he is only helping them because of the Command Spell forcing him to, and even then, he makes it clear he will continue to defy the Protagonist at every turn.

Trivia

 * The name Goetia or Goëtia is a practice that includes the conjuration of demons, specifically the ones summoned by the Biblical figure, King Solomon. The use of the term in English largely derives from the 17th-century grimoire The Lesser Key of Solomon, which features an Ars Goetia as its first section. It contains descriptions of the evocation, or "calling out", of seventy-two demons, famously edited by Aleister Crowley in 1904 as The Book of the Goetia of Solomon the King.