Here's why:
* Meg's confrontation with IT: Meg, Charles Wallace, and Calvin finally reach Camazotz and confront the evil force known as IT. Meg struggles against IT's influence and its attempts to control her mind.
* The power of love: Meg's love for her brother and her determination to save him fuel her strength. She uses the power of love and her own unique personality to resist IT's control.
* Charles Wallace's sacrifice: Charles Wallace, already under IT's influence, makes a heartbreaking sacrifice to help his sister. His act of selflessness allows Meg to focus on her mission.
* The defeat of IT: Meg, fueled by love and determination, finally manages to overcome IT's power, restoring Charles Wallace and freeing Camazotz from its influence.
While there are other intense moments in the novel, Chapter 10 marks the turning point in the story, where the protagonists finally face the central antagonist and the fate of the universe is at stake.