Gau (ガウ?) is a feral child who lives among the animals on the Veldt, having survived in this harsh environment nearly his entire life. His powers of speech are poor, barely capable of communicating with others and often growing frustrated with complex sentences (in the Japanese version this frustration is further exaggerated). Initially encountered by Sabin and Cyan, Gau is tempted into the party with a slab of dried meat and returns the favor by presenting the pair with Mobliz' missing Diving Helm, enabling the trio to survive the underwater current of the Serpent's Trench and eventually reunite with the Returners.
Gau is again encountered on the Veldt in the World of Ruin. In this second part of the game his origins are more thoroughly explored - by taking him to the old man in the lone house west of the Veldt where Sabin's sub-plot first began in the World of Balance, it is learned that this man is, in fact, Gau's father, having tossed him into the wilds shortly after the death of his wife in childbirth and consequently labelling Gau a 'demon child.'
Gau's class is best described as a reinvention of the 'Hunter' from the previous game. As the party travels around the Veldt, enemy groups from every area in the game are encountered. Gau's 'Leap' command appears only while on the Veldt - selecting it enables Gau to learn how to mimic the attacks of the monster set he leaps to and returns with in a later battle. The 'Rage' command locks Gau into an attack pattern drawing directly from the selected monster in addition to granting him that monster's unique statuses and resistances, if applicable.
Gau can learn magic, and remains under manual control so long as magic attacks are selected each turn. He does not possess a hidden special attack, as he doesn't use an 'Attack' command.
Gau's youth, boundless energy, vulnerability, and generally positive personality made him the first of several "energetic young boy" characters, which set the stage for the characters of Zell, Vivi, and Hope. -Wikipedia page. LOL.