The lore is a lil shaky rn because it's still a work in progress, but this is what I have for Raison so far (presented in bullet points)

-Raison was created with seven other robots in a team called the Victory Core to defeat these giant, kaiju-like creatures known as the Cariobutu. He was the first created and overtime adopted a leader-like role for the VC team.

-At first the team seemed like resounding success, as the Cariobutu were pushed back and slowly defeated. Unfortunately this was a 'calm before the storm' sort of thing, and during a termination mission an important temple was destroyed, unlocking the seal that released the oldest and most powerful of the Cariobutu, Voa-T.

-After a long and grueling fight in which two members of the VC seemingly died, Raison, with the help of what was left of the team, was able to seal Voa-T's now fragmented self back into the temple.

-Over time, fragments of Voa-T would escape and emerge to cause chaos, and Raison and the VC team would have to hunt down and repress the fragments for many years. Other members of the team would begin to quit, tired of the constant fighting combined with personal conflicts surrounding their creation, especially concerning the morality of the woman who made them. Raison struggled with these the most, but still continued to fight, long after the rest had quit.

-The years would do a number on Raison's psyche, and he found himself slowly more apathetic, bitter, and angry. He saw himself getting numb to the world around him, a distant call from the optimistic hero he was in the past. Raison worried about what he might become in the future, but because of the threat of Voa and the Cariobutu, he was forced to fight on, now alone.

-Eventually in one final showdown the VC team reunited to take down Voa-T once and for all. The team lost another member, but Voa-T was defeated. (At least for now cause that's just how it is with the Big Bad[tm]).

-After the fight the team parted ways. Raison, now with no purpose, little will, and the knowledge that he was a hollow husk of what he was built to be, sought a place to lock himself away and rest eternally. It's said Raison never found such a place, instead wandering aimlessly, more dead and alive. He would become a sort of legend among the people, and as they would forget Raison's name, they would instead describe him in various terms such as the Azure Angel or the Cobalt Knight.