What is the twist about Gemma's powers in Insidious: Out of the Further?

The major twist about Gemma’s powers in Insidious: Out of the Further is that her ability goes far beyond merely entering The Further—a power already seen before in the franchise. She is revealed to be a rare type of person known as a Courier, someone who can literally bring entities (and even entire environments) from The Further into the real world—and in the film’s final act, she turns this ability “in reverse” to send rogue demons (and even the demon-occupied house) back into The Further, trapping the villain Cyrus and ending his threat.