Schaal has inherited from Will whatever genetic twist that allows someone to become an Incarnate
Will being recruited out of the blue, as well as Beatrice, indicates that you need something
special biologically to become an Incarnate. If just anyone could be an Incarnate, the Northern Army wouldn't have had to search out a professional singer or an orphanage director living in the middle of nowhere.
In episode 6, Miglielia tastes Schaal's blood from her injured wrist, licks it, and promptly goes "Bleurgh!". Miglielia being able to detect whether someone can become an Incarnate from the taste of their blood would explain why Cain keeps her around (and how he found, transformed and trained a half-dozen new Incarnates since the end of the war), and her enjoying feeding off blood might explain why she hangs out with a psychopathic vampire. It would also explain why Cain deliberately dressed Schaal in a gown made of Arachne's spider-silk, before he shot her to drive Hank into his Fenrir form, which would likely - and actually did - allow her to survive the gunshot. He wanted to keep Schaal alive in case he needed a spare Incarnate later.
There's also Schaal's Animal Motif of the butterfly, both in her hairclip and in the anime EP. The butterfly is synonymous with the concept of transformation, and could be Foreshadowing to Schaal drastically transforming later in the story arc.
Schaal's destiny is to find a cure for the Incarnates
In volume 8 of the manga, Schaal and Hank visit the Incarnate Research facility, Ecole, where Schaal passes out after hearing 'the Voice of God' - just as Elaine once did.
In the description for vol 9, note
the flashback to Hank and Elaine's pre-Incarnate days indicates that the Voice of God drove Elaine to create the Incarnate process
. If Elaine's destiny was to create the Incarnates, as instructed and driven by the Voice of God
, it could mean that Schaal's is to be the instrument that lets the Voice of God clean up it's mistakes. It's implied that Elaine left Ecole once the initial procedure was perfected - it's possible that if she'd stayed longer, the Voice of God would have instructed her on the cure as well.
Claude is really just begging to end up an Incarnate
He's hardly the only Fantastic Racist
in the series, but he is one of the most consistent sources from audience's perspective. For most, that's enough to make it very satisfying to see him walk a mile in the shoes of the men and women he's been killing like rabid beasts. Really with his history the subplot is ripe with all kinds of potential.