clue

Exploration Stage: Artifact Bank
From: Mr. Black
Description: I saw a statue in the bank with the word "clock" inscribed on it and a pedestal in the shape of a dial. Maybe there is a lever inside the numbers? I'll push it. Okay, the numbers are pushed into the floor and the cloak of the statue starts to move! I'll check it out right away!
Completed: Oh, right, this cloak is a mechanical message left by the guardians, reproducing someone's voice. Whose voice, exactly, is it out of the five? According to the voice, the guardians' vault is in the bank, and only a sextant can locate it. What in the world does this mean?