Regions

A region groups rooms and owns behavior for all of them: containing lists members (additive across lines; regions nest), an on every turn clause is a region daemon firing only while the player is in a member room, and after the player entering / after the player leaving bind to boundary crossings in either direction. leaving exists only on region blocks.

create the Grounds
  a region
  containing the Drive, the Hall
  landing the Drive

  on every turn while one chance in 6
    phrase night-wind
  end on

  after the player entering
    phrase cold-returns
  end after

  after the player leaving
    phrase out-of-the-wind
  end after

A region becomes a place once it says where things land. landing the Drive names the room that move … to the Grounds puts an entity in, and it is what the Grounds's location means. A list must say how to choose — landing, randomly: the Drive, the Hall — with cycling and stopping as the other two strategy words, drawn on the region's own seeded stream. One landing line per region, every room in it contained by the region (directly or through a nested one), and set the Grounds's landing to the Hall replaces the whole list with that one room. A region with no landing cannot be moved to, but is in the Grounds is a membership test either way: true in any member room, through nested regions, with no landing line needed.