DRAGON QUEST BUILDERS 2

Story related and cannot be missed.

After returning from Khrumbul-Dun, you'll be tasked with building a pyramid and oasis. After part of the pyramid is completed, you'll be attacked, and flee in the boat. This brings you to Skelkatraz.

Skelkatraz is different from the other islands, as there is virtually no building. It's a fairly linear story segment with some "stealth" and a tiny bit of fighting at the end. Once you've completed Skelkatraz, the trophy will unlock. You also can't return to the island, but there's nothing missable there.