A great reminder/introduction to just how vast the supernatural world is: Tamatoa is bigger than any house Moana has seen, and he lives in a giant clamshell
Tamatoa’s expression of terror when Maui takes hold of his hook for the first time shows just how powerful and feared Maui was back in the day. It proves that “You’re Welcome” wasn’t just puffery and showing off.
Setup for an ongoing difficulty/twist: Maui’s inability to use his hook’s powers like he used to, and his sense that without his hook, he’s nothing.
The sense that Maui isn’t the only one who thinks he’s nothing without his hook: Tamatoa agrees.
Demonstration of Moana’s fear when faced with the supernatural world, then her courage to recover, and her resourcefulness to trick Tamatoa
Revelation the Maui was abandoned at some point, feels alone, and does great deeds for humans mostly to feel wanted and accepted
Moana saves Maui, which elevates her to his level, and puts them on more equal footing.