Over level 500.
Contracted the first year of the incursion.
Started as a yellow, changed to white after three years by using her yellow's wish.
Extensive explanation in ch.36.
Saintess's signature magic allows her to rebuild her body if it is destroyed and she has enough mana. She has died many times. Many, many times.
Mikasane explained this on discord: "It's actually a type of semi-temporal magic. Basically, if my physical body is destroyed or I want to activate my Signature, my magic rewinds my soul back to my last checkpoint. From there, my soul's "memory" of my physical state when I was at said checkpoint is reinstated using mana. I say semi-temporal because it only rewinds my soul's location back to the last checkpoint, not it's state, which allows me to keep my memories of what happened." (Discord, #mgg-general, 2/6/2024 8:30 AM)