SAI was thought up on the spot a few days ago. I was posting on Reddit in a subverting common fantasy tropes thread and came up with "What if we started as a fantasy story and it ended up something different?"
Paladin is an old Avatar concept from my Avatar sheet listing all of my intended Avatars. It originally started out as something closer to Kenji from For Honor and gradually changed into a English/French knight. It's fully designed to be a melee-centric mecha in a ranged combat era with guns and missiles.
SAI starts off as being seen from the Avatar's perspective. This particular Paladin-class Avatar is supposed to be very, very old, probably one of the first to be designed. That's why he sees everything in fantasy terms.
In my Aal-Ibrahim sub-universe, dragons are a super-family of extraterrestrial creatures from a neighboring galaxy, spreading their genetics across the Milky Way. Most of them are apex predators, and on this planet, they get to massive proportions.
I don't think I'll add to this story and make it a longer, multi-chapter story.