Cave Oyster

Cave Oyster is a quest item that can be found by fishing in Desert Caves. It has no combat or building use on its own; its purpose is to satisfy relevant quests and related progression requirements that call for it.

Because it is obtained through fishing rather than combat or mining, the most direct way to get one is to fish in Desert Caves until it appears. Since it is a quest item, it is worth holding onto when found instead of discarding it, even if you do not immediately need it.