I couldn't finish 'em. Looks like this's gonna get complicated.
Gigas is an enemy in Final Fantasy Dimensions. It is encountered in the Challenge Dungeon of the Prologue part. Since the Challenge Dungeons do not appear outside the original phone release, it is only dummied in the other mobile versions and therefore not available in any English version of the game.
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.