Recently I have realised that both kaeris and cryd control fire this discovery made me come up with a alternate backstory, here it is.
what if at one point kaeris and cryd were sisters, however when they entered the breach, they felt a surge of magical energy flow through them (like Hoffman an Ryle in breachside broadcast) Sonnia was left incapacitated whereas anasalea was left physically unscathed. Worried for her sister, anasalea took her too a surgeon who she hoped could help. This doctor was victor ramos the arcanist master. He commenced an operation to save sonnia. In the end Ramos had succeeded but sonnia's face had to be protected by an iron mask (the on sonnia still wears to this day). When sonnia regained consciousness, she was disgusted by what anasalea had let Ramos do to her. She quickly fled the scene.
ramos then took anasalea as an apprentice to show anasalea her potential and help develop her mechanical wings.
from that day on sonnia had a sworn hatred for the arcanists and joins the witch hunters in order to track them down. She even went as far as to change her name to sonnia cryd. This explains whey both an arcanist and a member of the guild both have the same magical abilities and how sonnia got her mask.
note this is not what really happened and is just a reimagining.