Stone of Summoning

Exploration Stage: Heirs' Villa
From: Robert Luxmore
Description: The scroll says that the Luxmore clan can be summoned by a stone. But we have only ever summoned servants with a doorbell...yes! Oh, by the way, there was a special doorbell with crystal decorations. Where did I find it...
Completed: I am sure it is that doorbell. It was in my father's study, but I had never rang it. But let's take this opportunity to ring it. Did you hear that? It's as if something is resonating...