Diablo 4 - and in fact the entire Diablo series - takes place on an entire planet, rather than the flat plane that the games' isometric perspective makes it appear they're set on.
In a tweet, Harrison Pink, senior quest designer on Diablo 4, offers to share a "tiny lore nugget," stating for the record that "Sanctuary is a planet. I don't know if we've ever officially stated it or not, but it's 100% a spherical celestial body with at least one moon, not a flat plane with edges."
On this #DiabloIV day of days, I think it might be fun to share this tiny lore nugget: Sanctuary is a planet. I don't know if we've ever officially stated it or not, but it's 100% a spherical celestial body with at least 1 moon, not a flat plane with edges.June 5, 2023
Pink said that their discovery of this nugget came during the creation of Waxing Gibbous, a unique axe available for Diablo 4 Druid Builds, which comes with flavour text that describes "the nights preceding the full moon." Presumably, in order for a moon to be full, it would have to be in shadow at other points in its orbit, and both shadow and orbit would imply the existence of a celestial sphere.
If I'm honest, I don't know why I'm surprised. Sanctuary is extremely large, and other than the camera trickery that Blizzard employs, there's no reason to suggest it's anything but its own planet. A few lore-curious folks have shown up in the comments beneath Pink's tweet to ask about the physical laws governing this discovery, but Pink points out that Sanctuary still exists in its own pocket dimension where anything goes.
One other fan, however, has asked what exactly Pink's comments might mean for the two Diablo 4 expansions. Those were revealed by Diablo lead Rod Fergusson over the
Read more on gamesradar.com