Darinius' backstory is kind of short since for a 1st level character I prefer to sketch out some characterization notes to start RP rather than have a whole book of backstory for a 1st level character like a lot of people do.
Darinius has a huge inferiority complex about having an obvious draconic heritage but not yet being able to cast spells, since he has bloodline abilities but no caster levels yet. Does not particularly like other arcane spellcasters therefore and tends to be snarky about it. He tends to be a little nasty at first but then should warm up.
The only clue that Darinius really has about his heritage is that it might have something to do with Tian Xia. Therefore he tries to get the attention of people who might know something about that part of the world by trying to speak Tian, even though he does not really know the language and only has a Tian-Common dictionary to go off of.
He also has been borderline badgering Amieko and any other Kaijitsu siblings since they stand out as Tian. They probably have not taken notice of him yet, beyond the fact that he is being kind of weird about it.
Exiel might have something to say about Darinius’ spear and Darinius may or may not know this.