"It was you guys who stole the power of the Thunder God!"
Peter kept recalling these words in his mind. This was the last thing the monster had said to Anna. It meant that the monster's consciousness was most likely the consciousness of Anna's father.
As for why the consciousness of Anna's father had appeared in the illusion, this was what Peter wanted to find out.
After Anna's consciousness escaped the illusion, she began to fall into a coma. Meanwhile, her distorted body finally returned to normal. This made Peter think that the illusion had an effect on the insects inside her.
Peter tried to get close to Anna's body to check if anything dangerous had happened. At least the tentacles that appeared behind her had stopped squirming.