Gortash invited you into his Audience room to speak to him.He offers a proposal - so long as the party does nothing to harm him, they will be kept safe from his Steel Watch and can move about the city freelyDoing so could make your stay in Baldurs Gate much easier especially if you only have to deal with Orin. Now the deal is that youll be focusing entirely on her and once you have her Netherstone you can bring it to him and reign the Elderbrain under your control.