Pirates, a camphor tree spirit and a river dragon

Our adventurers decide to venture towards the center of the island looking for the temple of the Opiwang (dead spirit king). From a rudimentary map they visit a pirate encampment marked on the map, only to find the encampment was completely destroyed except for an ancient shrine and plenty of undead. Along the way they find a camphor tree whose essence carries a powerful spirit who aids the party in many ways. After battles with giant spiders, spider trolls and oni, they meet a powerful river dragon who carries the party to the wastelands of the Opiwang where a temple is located somewhere within.