Guardian Force

Guardian Forces are the summoned creatures/monster of Final Fantasy VIII, and they are used by junctioning them to a character.

It is stated in-game that long-term junctioning of Guardian Forces causes memory loss to the user, so using them is not without risks.

Quezacotl
Quezacotl is one of the GFs given to the students of Balamb Garden. It uses a thunder attack called Thunder Storm. It is fairly weak and is primarily used for its Card Mod ability, which allows the player to refine Triple Triad cards into items, and the Card move, which can turn weakened enemies into cards (which can be used to refine). It is able to refine items into Thunder magic and low-level magic to mid-level magic.

Shiva
Shiva is the other GF given to Balamb students. Her attack is a ice-based attack called Diamond Dust. She is also fairly weak but her Doom ability can be used to kill stronger enemies that are vulnerable to Death magic. She is able to refine items into Ice magic.

Ifrit
Ifrit is a GF who lives in the Fire Cavern, not far from Balamb Garden. It is the objective of the pre-SeeD exam to defeat Ifrit within a chosen time limit. Upon defeat, Ifrit decides to join Squall due to his strength. Ifrit is the strongest GF you get for a while. He uses a fire attack called Hell Fire. Ifrit is useful due to it's strength increasing abilities such as Str+40% and Str Bonus. He can refine items into Fire magic and items into ammunition for Irvine's limit breaks.

Siren
Siren is the first GF that must be drawn from an enemy. You can draw her from Elvoret during the battle atop the Communications Tower in Dollet or from Tri-Point in Ultimecia's Castle if you missed her. She uses a non-elemental attack called Silent Voice that does moderate damage and induces silence upon the enemies that are susceptible. She is used for her Move-Find ability (reveals hidden save/draw points) and her Mag Bonus. Another ability of Siren's is Treatment, which cure status ailments. She can refine items into Life magic, Life medicine, or tools (for upgrading and refining).

Brothers
Brothers is a pair of GFs named Sacred and Minotaur that make their home in the Tomb of the Unknown King. If you defeat Sacred in combat, he will call Minotaur to help him and both must be defeated before they will join Squall and Co. He uses an earth-based attack called Brotherly Love that will not affect flying enemies. His top abilities are HP+80% and HP Bonus, but also has Defend, which allows a character to defend, and Cover, which allows a character to defend a low health ally. Brothers is the first GF that cannot refine anything.

Diablos
Diablos is a GF that lives in a magic lamp. When the item Magical Lamp is used, Squall will be transported to a battle with Diablos. Upon defeat Diablos will join you. He uses a gravity attack called Dark Messenger that does damage equal to Diablos' level in percentage to the enemies max HP. Notable abilities are Darkside (sacifice some HP to increase Str.), Mug (steal when attacking) and Enc-Half/None (deceases amount of random encounters). He can refine items into Time or Status magic.

Carbuncle
Carbuncle can be drawn from Iguion in Deling City before fighting Edea or from Krysta in Ultimecia's castle if you missed it. Carbuncle's attack (Ruby Light) does not do damage, rather it casts Reflect on your entire party. Carbuncles important abilities include Vit Bonus, Counter (enables counter-attacking), and Auto-Reflect, which automatically casts reflect on the junctioned party member. It can refine recovery medicine from items.

Leviathan
Leviathan can be drawn from NORG after opening the pod or Trauma in Ultimecia's Castle if you missed it. It uses a water element attack called Tsunami. Leviathan's boost option is easier to get to max than the previous GFs. It has useful abilities including Spr Bonus, Auto-Potion, and Recover. It can refine items into Support magic or GF recovery medicine.

Pandemona
Pandemona can be drawn from either Fujin during your battle with Raijin and Fujin in Balamb or Red Giant in Ultimecia's Castle. It attacks with a wind-based move called Tornado Zone. Though not as powerful as other GFs, it is the first GF to give speed increases. It also has Absorb, which takes HP from the enemy and gives it to the castor, and Initiative, which lets the junctioned character start the battle with the attack guage full. Pandemona cannot refine anything.

Cerberus
Cerberus is standing in the main hall of the Galbadia Garden during the Galbadia Garden assualt scene. He must be defeated in combat for him to join. If you missed him, he can be drawn from Gargantua in Ultimecia's Castle. Cerberus' "attack" is called Counter Rockets and casts double and triple on all party members. Because of his Auto-Haste and Spd Junction abilities, he is useful for quick magic users. His Expendx2-1 ability makes it so double only uses one magic instead of two. Along with these, Cerberus also has the Alert ability which makes it so your party cannot be back-attacked. He also cannot refine anything.

Alexander
Alexander is a giant machine that must be drawn from either your second fight with Edea in Galbadia Garden or Catoblepas in Ultimecia's Castle. He uses a Holy attack called Holy Judgement which is very useful against undead enemies. Due to it's holy nature, it is good with healing. This is reflected in the abilities Revive, Med Data (increased effects of medicine), and Med LV Up (levels up medicine). It can also refine Mid-Level magic into High-Level magic.

Doomtrain
Doomtrain is a train GF that must be assembled by aquiring a number of items and the Solomon's Ring. Doomtrain's attack, Runaway Train, does minor poison damage, but also inflicts every status ailment and deplets vitality. It has the abilities Darkside and Absorb (from Diablos and Pandemona, respectively) plus Auto-Shell and Junk Shop, which calls the weapon upgrading shop from the menu. It can also refine items into Forbidden medicine.

Bahamut
Bahamut is a powerful GF that must be fought in the Deep Sea Research Center to acquire. Two Ruby Dragons must be defeated first, and a hidden option must be selected afterwards. His attack, Mega Flare, inflicts major non-elemental damage on all enemies. It has Diablos' and Cerberus' abilities Mug and Expendx2-1 as well as Auto-Protect, Move-HP Up and Rare Item, which increases the chance of getting a rare item from battle. He can also refine items into powerful Forbidden magic.

Cactuar
Cactuar is aquired by defeating the Jumbo Cactuar on Cactuar Island. His 1000 Needles attack does 1000 extra non-elemental damage for every ten levels he gains. He is notable because he has HP, Str, Vit, Mag, and Spr Bonuses. He also has Pandemona's Initiative, Leviathan's Auto-Potion, Cerberus' Expendx2-1, Bahamut's Move-HP UP, Brothers' Defend, as well as his own Kamikaze. He also has Eva and Luck increases.

Tonberry
Tonberry will join your party if you defeat Tonberry King, but to fight him, you must defeat 20 Tonberry's in a row. His Chef's Knife ability does minor non-elemental damage. He has the LV Down and LV Up abilities which decrease or increase the power of the enemy for decreased or added bonuses. He also has Initiative, Move-HP Up and Auto-Potion from previous GFs. He has four shop related abilities: Call Shop (visit a shop from the ability menu), Haggle (get a discount at shops), Sell-High (increase selling price), and Familiar (buy rare items in shop).

Eden
Eden can be drawn either Ultima Weapon in the Deep Sea Research Center or Tiamat in Ultimecia's Castle. It is the most powerful GF in the game. It's attack is a solar attack called Eternal Breath. It has the previous abilities Mad Rush and Darkside as well as a new one, Devour, which can be used to eat enemies. It also has Expendx3-1, which only uses one magic instead of three for triple. It can refine items into GF ability items.

Non-junctionable

 * Odin
 * Gilgamesh
 * Boko (Chocobo)
 * Moomba
 * Phoenix
 * Mini Mog