[He nods.] The problem with fonons is that they're naturally drawn to one another, and to perform an arte requires a fonist to gather fonons into their own body. If the contaminated fonons were pulled out of my body, any seventh fonist in the area could be at risk for becoming contaminated as well.

[Which is the last thing he wants to see happen.]

...but perhaps... if it wasn't a fonic arte protecting them, the fonons might not be able to register the castor as a source. Then the fonons would have no place to go.