Guardian Force (or GF) are entities of great power that can be summoned into battle to inflict a great deal of damage to enemies and are equipped by Junctioning them to a character.
The GF can also learn abilities that do a variety of things such as allowing you to Junction magic to increase stats, inflict or defend against elemental attcks and status effects and even find hidden Draw Points and Save Points.
A Guardian Force is a being of energy and when Junctioned to a Human, the GF will lose its physical form and can then be summoned by the Human for a limited time; in terms of gameplay, this takes the form of an ability from the GF. These abilites can either be offensive attacks or positive status effects for the party.
There are 16 GF's that can be Junctioned to your party and 6 that cannot be Junctioned. Additionally, there are 2 GF's that only appear as enemy summons.
Odin:
Odin is a warrior who, through the rain, appears riding a six-legged horse with white, pupil-less eyes.
He wields a sword called "Zantetsuken" which translates as "Iron-Cutting Sword".
He will randomly appear at the start of battle to dispatch enemies with a single blow.
He can be obtained in the Centra Ruins from a Side-Quest.
Gilgamesh:
Gilgamesh is a warrior wearing a red, tattered cloak. He has white, pupil-less eyes and grey skin.
If you have Odin before fighting Seifer in Lunatic Pandora, Odin will attack Seifer but be cut in half; his sword flying into the sky and into the hand of Gilgamesh. During the fight, Gilgamesh will appear and blow Seifer away.
It is implied that this Gilgamesh may be the same one from Final Fantasy V; while searching for Excalibur he ends up in the "Interdimensional Rift" which Gilgamesh mentions in his dialogue here.
He has 4 different attacks, each using a different sword.
Phoenix:
A legendary bird of fire that appears when a Phoenix Pinion is used; it deals Fire-Elemental damage to all enemies and revives KO'd allies in battle.
The item cannot be bought, but can be found/obtained as a reward in certain quests and refined from Mega Phoenix.
Boko:
A Chicobo that can be summoned using Gysahl Greens while in battle.
Boko can be levelled up in Chocobo World which originally required an add-on for PlayStation called PocketStation which was only released in Japan. On PC releases, the mini-game was included.
The first time you go to a Chocobo Forest and catch a Chocobo, ChocoBoy will give you Boko.
Moomba:
Moomba's are a small, furry creature used as slave labour but the Shumi believe them to be Shumi who have not become Elders.
In Chocobo World you can obtain an item called "Friendship" that can be used in battle to summon a Moomba. (In the remastered version on PC, this is gained from Angelo Search)
The Moomba will reduce an enemy's HP down to 1HP unless they have more than 9,999HP; then it will do 9,999HP damage instead.
MiniMog:
MiniMog is a Moogle with a more feline appearance.
MiniMog can be summoned after obtaining the Mog's Amulet from Chocobo World (Angelo Search in FF8 Remastered). This can be used to teach a GF the MiniMog ability which gives the MiniMog command in battle.
MiniMog, when summoned, will heal your GF's and revive fallen ones for a price in gil; your party's average level multiplied by 100.
