Why does Joan come to fear Ogun in the novel, That Self-Same Metal?

While Ogun seems dismissive of his subjects' wills - as shown by his numerous possessions of Joan- it is implied that he is protecting her. Unfortunately, this leads to Joan fearing him and worrying that she will lose herself. Ogun temporarily seals his power from her, only returning once she asks his forgiveness and accepts his blessing to kill Auberon.