Sounds like (according to a flowery blurb in the Larian Gazette) BG3 will have a protag mechanic very reminiscent (if not outright similar) to the Spirit Eater mechanic of NWN2: Mask of the Betrayer.
"You are burdened with a great power devouring you from within.
How far down the path of darkness will you let it take you?
The fate of Faerûn is on your party’s shoulders.
Will you carry it to salvation, or descend with it to hell?"
At least at a descriptive level, sounds VERY similar to the Spirit Eater.
Mind flayers are the big thing in this game so I am guessing you are 'infected' somehow by mind flayer semen and are trying not to 'succumb' to it.
