The child who is prophesied to save Faerie Britain. She is a special faerie who, along with the Staff of Selection, was dispatched to the surface world by the planet's inner sea, Avalon. After she drifted to the lake region, the chief of the Mirror Clan decided to send her off on a boat loaded with numerous treasures, after which she reached the coast of Tintagel, where she was raised.

In the Lostbelt, she is the counterpart of the girl who would come to wield Excalibur in Proper Human History. She was sent to collect information from the surface in order to forge the Sacred Sword, a powerful weapon against threats to the planet.

An innocent, energetic, and ordinary girl who hates to lose, is strong enough to take a hit, values the importance of reading the room, and hides her true feelings from others. She is a practical researcher who spends her days studying magecraft in some truly animated fieldwork.

She is the protagonist of this story who, to meet the expectations of others as the Child of Prophecy, sets off on a journey to save Britain.

...But that is only the face she presents to the world.

Artoria of Proper Human History was honest and forthright, but the Lostbelt Artoria is not as strong-willed; she is frail, timid, and a pessimist. Internally, she sighs in exasperation at the foolishness of being the Child of Prophecy, as well as at the self-destructive tendency of so many in pinning their hopes on a prophecy. (She's neither dispassionate nor dismissive of their plight. Thinking about it just kind of gets her down.)

Since Artoria is always concerned with the feelings of those around her, she is unable to express her own true feelings. She does not want to hate or come into conflict with others, so she tends to just agree to do what is asked of her in whatever way she's expected to behave. She works very hard because the truth is that she is clumsy, makes a lot of mistakes, and is constantly stumbling on her journey.

The one thing she is truly good at is getting right back on her feet, which is why she's constantly making apologies for being so weak, and promising to do better. Every time she makes these promises though, she finds herself thinking about how terrifying fighting is, how exhausting hatred is, and how wonderful it would be to just live an ordinary life.

Artoria may be her own harshest critic, but no matter how bad the environment around her, or how badly she's treated, it is not in her nature to give in to evil, forget her manners, or stop caring around the people around her. And that is proof of just how truly noble in spirit she is. That very trait was also the crucial difference between herself and Oberon.

One might expect a Child of Prophecy on her pilgrimage to do everything she could to help others, even if it's scary. The truth, though, is that the Child of Prophecy set out on her journey to do her best, because she knew people would be disappointed if she was frightened.

She always conceals her deeply negative feelings. "Everyone is scary, society is nauseating. I don't have any motivation to save the world, but I also don't want to go against the people around me, so I'll try to be their savior."

Despite that, her deeds appear noble in others' eyes, seeming a worthy equivalent to King Arthur's way of life. In truth, though, Artoria Caster is obsequious, reactionary, and pessimistic. So she constantly criticizes herself, thinking, "I pulled it off this time, but I'm sure they'll sack me the next time around."