Moonlight.
For all that it appeared to be nothing but the counterpart to daytime, it was the irremovable key of Kaitou KID's magic.
Were it not for the silverly gleam of light creating depth, there would be no shadow to use for deception, no soft glow to utilize, replicate and disappear in.
But most of all, it is only thanks to the illuminating Lady Goddess that a gentleman thief has someone to ask about the state of his quest.