The biggest objective of Corey's plan was to ensure that the world tree did not perish, and that she would be able to fight Anton all by itself.
The world tree was as powerful as an Immortal, and since Syrelle was occupied by Thalos, he needed the world tree to fight Anton.
Although Corey had no idea if the world tree could defeat Anton, but for Corey, as long as Anton was occupied, he and Pamela would deal with the priest and mage.
However, the world tree transmitted to Corey that she was fearful of the book in Anton's hands since it felt like Anton was holding a true piece of death with him.
She also told him that she knows that although she might have a lot of power, her combat abilities were limited.
Compared to humans and other creatures that could move, her physical structure was not built for combat. She was meant to nurture her world, and her ability to control storms and lightning was just to defend herself.
