Gigas Worm is an enemy in Final Fantasy Dimensions. It can be encountered on Mt. Rusalka. It's the enemy that has the highest HP in this area. This monster can hit quite hard but it's not very fast and can be defeated easily with continuous attack and powerful spells.
Gigas is a popular term for races of giants in fantasy games. Gigas is a Greek word meaning "giant," originally used to describe the race of Gigantes in Greek mythology and is used in the scientific name, as the specific epithet, of hundreds of species of animals and dozens of plant species to denote their size.