Add a new Dynastic Rule to the Ruleset. Call it “Starting Room” and give it the following text:

If there is no Room named “Foyer” in the Mansion Map, the Narrator may create such a room and immediately add it to the Mansion Map. It shall have the default value for all of its non-name variables. When that room is created, all Explorers automatically move to it. The Narrator shall then destroy any Rooms named “Foyer” that are not represented in the Mansion Map.

If there is a Room named “Foyer” in the Mansion Map, the Narrator can and should repeal this rule.