What is the significance and importance of cavern scene in macbeth

It is where MacBeth draws all the wrong conclusions. He should learn that Banquo's issue will become kings and not his. Moreover he hears that he should fear MacDuff. Nevertheless he disregards that warning since he doesn't have to fear anyone born from a woman and needn't fear anything until the forest comes knocking at the castle gates.

How is this a turning point? Before MacBeth was somewhat squeamish and had his wife ballbusting him into manning up. From hereon those roles are reversed. MacBeth feels invincible and Lady M. is losing it. Is there a role for Hecate? Well, she is present. There is something ominous about her claiming that the witches stand to gain here. Moreover, you could argue that it is she who presents the apparitions and the visions to go with the witches' predictions. She's the boss, neh?