Leukos is, according to the reveal, an academy in Xenoblade Genesis where students train to become Vesselai, the warriors who can wield Anima. This detail comes from the reveal trailer and surrounding coverage rather than Nintendo's official page, so it should be read as preliminary.
Overview
Leukos is a place of learning for aspiring Vesselai. Japanese coverage describes it both as the school that trains them and as the place where first-rate Vesselai gather, which frames it as a selective institution rather than a general school. Its full name in Japanese translates as the Vesselai academy Leukos, which settles a question earlier coverage left open: Leukos is the name of the institution itself, not a region or a wider place name. Some English reporting described it more specifically as a military academy, but the Japanese name carries no military element, so that characterisation should be treated as a gloss rather than a description of what the school is. Leukos and the land of Anshar are the only two named places so far, and Leukos is the only named settlement or institution. See Setting and World for the land itself.
The Academy as Shown
Nintendo's official screenshots include an interior view of the school. It is a long vaulted hall of pale stone with tall arched windows, iron chandeliers, and rows of wooden benches and tables laid with candlesticks and fruit bowls, and it is busy with students in matching dark uniforms trimmed in blue, with the protagonist walking between the rows. It is the clearest look so far at Leukos as a physical place. Nothing in the shot names a room, a faculty, a house system, or a year structure, so none of that should be read into it.
The Protagonist's Path
The reported protagonist, Eleanor, is shown enrolling at and studying at Leukos as part of her journey to become a Vesselai. At least part of the story appears to follow her time and tutelage there.
Crystones and Daily Life
An Anima crystone is used throughout life in this setting, in academic contexts and beyond. Since these stones amplify a Vesselai's power over Anima, their presence at Leukos fits the academy's role as a training ground. The narration ties a student's whole time at the school to the stone, academic work included, which suggests the crystone is meant to be read as a record of a person's schooling rather than only as a weapon component. Japanese coverage of the reveal describes the stone as something the academy hands to a student, who is then told to wear it through academy life, so at Leukos it reads as standard issue rather than a personal acquisition.
What Is Not Yet Known
The reveal does not detail how the academy works as a gameplay setting. Whether Leukos involves a structured calendar, social systems, or any school-life mechanics has not been confirmed. Some coverage compared the school framing to other games, but that is commentary on the reveal, not confirmed design. No such systems should be assumed for Genesis until Nintendo shows them. These details are deferred.