Depends on the setting and game honestly. In DOS2 I played as Lohse, and I was deeply invested in helping be rid of her demon because I cared about her as a person and the feeling of sheer terror and horror whenever the entity took control really unnerved me. She's a light-hearted girl who was dragged into a horrible situation, so I am invested in saving her. Working alongside my party of Sebille, Beast and the Red Prince made me realise that they were my friends supporting me despite the fact I had a demon puppeteering my body around made me want to help them in turn, because they were my friends.
Obviously the main objective to start within BG3 is get rid of the tadpole asap. Once that that sword of Damocles has been solved then I will have time to take a breath and ponder. Why was I infected? Why did the normal symptoms not happen as per the norm? Can I trust these new friends and allies of mine? Should I help them and can they help me? What should I do now? Hopefully, when we learn more we will be to form our own motivation as the story unfolds.
