Well, if you look broader, all of the companions have a figure in their life that they are fixated on, be it Mystra, Mizora, Cazador, Shar or Vlaakith. I think this is because of the origin stories being custom tailored to the main plot of the game. My guess is that the absolute will use that figure to try to bring the companions to its side.
So whether Gale talks about his goddess ex-lover while Shadowheart about her devotion to Shar, or Astarion about his hatred towards Cazador, they all might face the same turning point when the party confronts the absolute.
