The Gi tribe was a tribe that used to live in the world of Final Fantasy VII who waged war against the citizens of Cosmo Canyon many years before the events of Final Fantasy VII. The tribe seems to have designs reminiscent of the Native Americans.
In the year 1959 according to the storyline of Final Fantasy VII, the Gi Tribe started an attack on Cosmo Canyon, whose predominant inhabitants at the time were the lion-like species Red XIII belongs to. During the attack, the Gi tribe attempted to use the caves, later known as the Cave of the Gi, to sneak into the town. Seto, the father of Nanaki (later known as Red XIII) who was only born earlier that same year, hatched a plan which would see the Gi Tribe defeated: he lured them into the cave, which was then sealed behind him. He knew that by doing this he would perish, but the sacrifice had to be made to protect his family and the village.
The Gi were unrelenting and attacked Seto with poisonous darts. He fought as long as he could, but succumbed to petrification and was turned into stone.
48 years after the victory, in the December of 0007, Red XIII visits Cosmo Canyon with little knowledge on the war on the Gi Tribe. Bugenhagen, a resident of Cosmo Canyon during the battle, unlocks the Cave of the Gi when he feels it is time for Red XIII to learn the truth about his father. Inside, he fights the spirits of the Gi Tribe, who are still lingering.
Before reaching his father, Red XIII fights the leader of the Gi Tribe, Gi Nattak. With his defeat, the Gi Tribe fades away and becomes a distant memory.
The Gi are fought during Final Fantasy VII in spirit forms. Gi Spector enemies are fought throughout the Cave of the Gi. At the end of the cave, the leader of the tribe, Gi Nattak, is fought. Gi Nattak is fought with Soul Fire enemies, which have the power to possess party members. The battle is reminiscent of the boss battle with Wrexsoul in Final Fantasy VI, which also possessed party members and had two accompanying enemies like the Soul Fires, called Soul Saver.