Cave Holes appear in the Caves. There are treasures in each Cave Hole. The items inside cannot be picked up directly, using The Lazy Forager is the only way to pick them up. The Ruins can be regenerated by killing the Ancient Fuelweaver, so by killing the boss over and over again the player is able to farm the Cave Holes for loot.
The Lazy Forager is often considered as a relatively expensive item to create therefore it may be situational as to whether a player wishes to create one to be able to collect the item.