The seven nations are failing the usurpation trials and the hallowing is spreading across Teyvat. Noy becomes increasingly unhinged seeing everyone dying around him and refuses to accept he couldn't protect Snezhnaya. He finds you, the last human alive in the ruins and takes you to his castle in a pocket of the shadow realm where the hallowing can't reach.

His mind is fracturing and he believes as long as he can keep one human alive then he hasn't failed completely.