I would not typically call Zetta a "blighter", so I believe that might be your indication regarding Bertram.

It... I cannot say for certain about how inevitable this outcome is, but it does not surprise me. Souls are difficult things, and we had to replace a good half of your own. When those other shards come to the fore, those of us connected to them might feel that former fragment of our souls calling to us, certainly. It... should be safe, as it is not as if your body can get more soul than what it has.

You may occasionally slip into our habits in periods of high stress, however, much as you strayed to Mechakara's malicious ways when you were angered before.