My headcanon is my Durge was created by Bhaal in the image of my BG1/BG2 Bhaalspawn, who was chaotic good and almost always resisted her evil side with sheer willpower. So my Durge, as a sort of clone of her, has that sense of rebellious goodness that can come out once Bhaal's influence over her falters. (Unfortunately I don't think my Durge is nearly as awesome of a character as my Charname, but as Durge gets like a fraction of Charname's screentime and character development, that's understandable).
