From The Heretic Knowledge Vault
Here there be half-elves. Ian is from Santuariel, but has been tremendously close-mouthed about its actual location. His travel plans imply that it lies to the north, beyond the confederacy states. It's somewhere close enough to Salvus for it to be reachable via horse- or ox-drawn cart, such as the one that Leah and Riley are driving (to drop a "load of junk" in Salvus) that Ian hops en route to his quest.
We don't know much about the place compared to some other Errant World locales. Ian describes it as "some damn hellhole that's practically a desert." Limited views suggest that it's set in terrain something like the southwestern United States -- New Mexico, maybe? The architecture fits; compare this view with images of Taos Pueblo, like this one.
Mages with healing skills are known to practice there, although the half elves' resistance to healing magic makes their job a hit-or-miss proposition. In the case of Ian's sister Evelyn, it's mainly miss, which is why Ian is off on his quest. Still, according to Riley, healing is a major source of income in town, which means that Ian's brand-new Omega-Heal skills might not increase his popularity with the locals looking to make a buck off the trade.
For a list of known, named residents of Santuariel, see Category:Residents of Santuariel. The place has been the subject of some Chronicles of Heretic Knowledge (here and here) that explains how it came to be what it is -- a long, sad story from the standpoint of its residents. Note that modern-day Santuariel is really "Santuariel V," the fifth place to bear the name and serve as a half-elf refuge.