Plot of Black Spine

So I’m reading a blog about the Adventure Black-Spine; believe it or not, I’ve never ran or played an official Dark-Sun adventure in my life; I always wanted to create my own adventure or play one that another DM created adventure.

So, on with the adventure; Queen Trinth is going to try and take over Athas, you know, Borys and Rajaat in the way, so she can take over the Lich-Queen because the Athasians are stronger and more wipey, this begs the question: If she and her army is strong enough to take over and enslave Athas, a people whom can conquer and enslave the Githyanki, why not just skip Athas and go after the Lich-Queen herself?