1. What’s their full name? Why was that chosen? Does it mean anything?
The only name Rias has is, well, Rias. I can’t say why the Tree picked that name, as her name actually has no meaning at all. I can say that I picked that name because the Descender in the manga version of the second Radiant Mythology game is named Roa, and once I saw that my brain wouldn’t stop trying to make similar names.
2. Do they have any titles? How did they get them?
Descender. It’s just what she is.
3. Did they have a good childhood? What are fond memories they have of it? What’s a bad memory?
She never really had one, actually. Rias was created at the age she appears to be now, with not a single memory in her head of anything, so you can sort of say that her first incarnation was sort of her childhood.
It was not good. She picked up right where the Descender who died before her had left off, and while she blissfully can’t remember any of it, it is where she got that large scar on her left side from.
4. What is their relationship with their parents? What’s a good and bad memory with them? Did they know both parents?
Rias’s parents are a tree, the same tree. Surprisingly she has an amazing relationship with the Tree, though, but only when she remembers what she is. The World Tree supplies her with mana to live, survive, and protect it, and considering that Rias is literally programmed to protect it at all costs...
She’s sort of forced to love it.
5. Do they have any siblings? What’s their names? What is their relationship with them? Has their relationship changed since they were kids to adults?
An interesting sort of question. There was a Descender before Rias, so in a way he could be seen as her sibling, but considering he’s dead... They’ve never met.
She also has lots of other siblings waiting within the tree to be born, y’know, in the event she ever fails and dies.
Really puts a damper on sibling affection.