Is there something more to this process that I am missing?
During the personal quests relating to Ysvelta and Tiachren, I picked the choice which allowed Tiachren one final attempt at saving her. You end up killing her because she cannot change. If you don’t pick this option, Tiachren will also become corrupted.
I understand that the nightmare court puts you through a lot of anguish and psychological torture and how that could traumatize or change an individual but I don’t quite see how their nature is quite literally corrupted to a point of no return.
Is this some biological thing where given enough time and pressure, they can corrupt any Sylvan’s resolve?