Protectors are a form of summons in the world of Final Fantasy XVI. Protectors are the offspring of relationships between Gods and Humans, making them demi-gods. The divine parents of Protectors were punished for disobeying the command of Olympus, and were thus Mechanised, becoming Guardians. Having been born, they were kept in hiding, but soon discovered and almost killed. Ultimately, the Protectors were crystallised into Crystals which can be used by the Lights.
At the birth of the 16th Cycle, 10 Gods came down to the human realms to interact with the creations of ages. Of these 10 Gods, 6 fell in love with humans and would go on to be known as Guardians. They wanted to take their human loves back to Pantheon and be with them, however, it was instantly forbidden by most of the Gods. Thus, the Guardians decided to procreate with their human loves against the wishes of Olympus, as an act of rebellion.
When the children were born, they were hidden from the view of Pantheon for some years by the collective protection of the Guardians. However, they are discovered and the Protectors and Guardians are arrested. Initially, it was decided that the demi-gods would grow up in confinement, but Olympus eventually decided, having been persuaded by Viha, that the children could be seized by humans and be used to usurp the Gods. So as to protect their power, the Gods decided to kill the demi-gods. To protect their children, the Guardians decided to fight back. However much they fought, it was in vain. Their children were taken and, as a result of their disobedience, the Guardians were Mechanised. The Protectors, on the other hand, were either given to their grandparents of placed back in custody. Finally, the decision was taken to crystallise them.
After they were crystallised, Ultima learnt of Viha's plan to steal the crystals, use it to summon the Protectors and them torture them till they became savants of Dark. So, along with her exiled son Prometheus, she stole the crystals and cloaked them in Light, so that Darkness could not find them and use them for evil. She left the Crystals in the protection of her son Prometheus, for safe keeping until the Lights appear.
Upon meeting Prometheus, Devi gifts the Lights their Light Powers. As part of their Light Trials, the Lights establish what value they fit with. The Protector with whom they shared the most is naturally drawn to that Light and so can be summoned to assist. Equally, each of the Protectors has an elemental affinity, which is garnered from their human parent, e.g. how Shiva's ice affinity stems from the fact her human father was an Eskimo, which matches the Elemental Affinity of their master.
In order to summon a Protector, Lights must conjure their crystals from Light and shatter them, releasing the Protector from its crystal chains.
List of Protectors
Ixion is Sky's protector. Ixion's father is the Guardian Odin, thus making his grandfather the Savior Raiden, and his mother was a warrior princess. Ixion's element is Lightning and he represents Strength.
Ixion takes the form of a knight, but can transform into the horse, Slephnir, in Gestalt Mode. His appearance was heavily influenced by Odin from Final Fantasy XIII.
Eos is Lola's protector. Eos' mother is the Guardian Leviathan, thus making her grandfather the Savior Famfrit, and her father was a sailor. Eos' element is Water and she represents Fluidity.
Eos takes the form of a fairy, but can transform into a winged dragonfly in Gestalt Mode.
Hashmal is Minim's protector. Hashmal's father is the Guardian Hecatonchier, thus making his grandfather the Savior Titan, and his mother was a tribes-woman. Titan's element is Earth and he represents Courage.
Hashmal takes the form of a feline man, but can transform into bipedal beast in Gestalt Mode.
Shiva is Zero's protector. Shiva's mother is the Guardian Seraph, thus making her grandmother the Savior Asura, and her father was an Eskimo. Shiva's element is Ice and she represents Beauty.
Shiva takes the form of an ice-covered woman, but can transform into a motorbike in Gestalt Mode.
Garuda is Storm's protector. Garuda's father is the Guardian Fenrir, thus making her grandmother the Savior Valefor, and her mother was a pilot. Garuda's element is Air and she represents Agility.
Garuda takes the form of a bird-like humanoid woman, but can transform into an organic-looking aeroplane.
Ifrit is Agni's protector. Ifrit's mother is the Guardian Brynhildr, thus making his grandfather Phoenix, and his father lived near a volcano. Ifrit's element is Fire and he represents Anger.
Ifrit takes the form of a beast like man, but can transform into a chariot.
Prometheus is Devi's protector. Unlike the other protectors, he is not a demi-god, but is in fact a true God. He wished to see Humans and Gods interact more. As a result, he took the power of magic from the Gods and distributed it to the humans - a crime for which he was to be destroyed. To try to save him, his father, the Guardian Alexander, offered to be Mechanised, to allow his son to live. The Gods, thus, made Prometheus a Protector - a human-like form with accented god-like powers - and transformed Alexander into a Mech. Alexander's father, the Savior Bahamut, has, since, always hated Prometheus, and even his mother, the Light Goddess Ultima, for what happened to Alexander, such that he exiled them from Pantheon.
Prometheus's is a non-elemental and he represents Justice. Prometheus appears to be an old man, but can transform into an eagle in Gestalt Mode.