Vermilion Bird explained it very clearly.
Warehouse Seven was a mysterious warehouse located right within Capital City.
Moreover, Green Dragon, Vermilion Bird, White Tiger and Black Tortoise, each had a key to Warehouse Seven.
Only by bringing the four keys together could Warehouse Seven be opened.
Only if William Cole truly agreed to become the Patriarch, would he have the qualification to open Warehouse Seven.
"You're forcing me to become the Patriarch!" William let out a bitter laugh.
Vermilion Bird shook her head, "We're not forcing you. It's your choice in the end. If you choose to become the Patriarch, we will use all of the Patriarch's power to find Ruth Dawn."
"If you don't want to be the Patriarch, we won't pressure you."
"I'll think it over," said William, noncommittally. Then he drove his smashed Rolls Royce back to Thirteen Hall.