[A physical symptom of corruption. In other words, something magic related, because when has it not been magic related? He's grown used to it by now at least.]

And since you're familiar with his degradation, I'm assuming you're the man responsible for his corruption. Afflicted some magic on him. [He seems less than impressed, but Hans doesn't pretend to be overly upset. He's trying to get information, for one, and this guy is important to Ferran despite being terrible in some manner.

Well, if he truly caused Ferran's current state, then that speaks for itself.]