The Man Who Can't Breathe

The Man Who Can't Breathe, sometimes called the Man Who Lives in the Vents, is the demon who haunts Quinn Brenner in Insidious: Chapter 3. He appears as a thin man with corpse-like skin in a hospital gown. He wears a breathing mask that covers his grimy and deformed mouth.

History
The Man Who Can't Breathe is first introduced when Quinn tries to contact her recently dead mother. He repeatedly terrorizes Quinn shortly after this; first distracting her from oncoming traffic which results in her breaking her legs, after which he pushes her off of her bed several times and tries to kill her by dragging her out into the window. The Man Who Can't Breathe lives in the apartment above the Brenner's which is supposed to be abandoned. He is able to possess people, which he will typically do to make his victims commit suicide. He does this because he wants to keep these souls as his "pets". He can also shape-shift into victims loved ones. He is defeated by Quinn when she pulls off his mask, making him vomit large amounts of dust.