Exactly. Purity is for geographic things. Essentially, permanent features put on the map. Settlements and such are a special case as we put them on the map, but they are paid in Prime and are not necessarily permanent.
And yes, the rules are the same for artifacts. It can be magical, but every time it actually does its thing, Prime needs to be spent. There is no magic in the world unless it flows through a god (and is paid in Prime).
