She is voiced in Japanese by Tomoyo Kurosawa, whom you may know for lending her voice to Christophorus in the Blade of Azure series, and Otome Arisugawa in the Aikatsu! series.
Below you can read an official description.
“Sothis is a mysterious being who appears in the protagonist’s dreams after saving them in FireEmblem: Three Houses. With no memories of her past and wisdom beyond her appearance, she speaks as though she lives within their head, but no one else is aware of her existence.”
Interestingly, on to of screenshots and artwork, we also get a video. While it’s in Japanese, she indeed talks in a rather old-fashioned way. It certainly gives the character some depth, even if it’s a trope that has become rather popular in Japanese media as of late.
You can check out both video and images below. If you want to see and learn more, you can check out a look at the main hero and heroine Beres and Beret, and more screenshots and gameplay details from this week’s issue of Weekly Famitsu.
Fire Emblem: Three Houses will be released on July 26 exclusively for Nintendo Switch.