Sunny was the only one who could prevent more people from silently walking into the cold ocean. Even if he returned the borrowed Memories and gave the Undying Chain to someone else, the other person would not be able to enjoy the augmentation of the four shadows. So, the mind hex would remain unbroken.
If there was one good thing about the situation, it was that after Sunny had rid himself of the hex, he did not need to keep up his mental defenses at such a high level anymore. It was as though he was now inoculated against the unknown creature's influence.
At least for now.
He returned the charm, the mercurial cloak, and the flint dagger to their owners. One shadow continued to follow Professor Obel, while the other three remained wrapped around the Undying Chain, just in case. After that, everyone got to work.