Giant Worms have a chance to spawn from the egg found in the Giant Tree nest. They destroy all solids while traveling, leaving tunnels that the player can move through. There is a risk that they will damage the Holy Mountain enough to anger the gods. The Worm Crystal reduces the chance of this happening by deterring the worm, but this may still happen on occasion.
While the small Worm is relatively easy to kill even with the starter wand, Giant Worms are much tougher, and deal 25 damage per bite. Their size lends them greater speed, which can get very lethal very quickly.
The largest Giant Worm will have a visible health bar, and will drop a Maximum Health Increase pickup when killed. This pickup will not be dropped if a second Giant Worm is killed.
These can also appear above the player when entering a new stage.(We are not sure if this is normal or simply a bug)