The Long-haired Fiend

The Long-Haired Fiend is the alias given to the spirit of a mysterious and violent man existing in the Further and acts a minor antagonist throughout the film.

Insidious
The Long-haired Fiend appears twice throughout Insidious. In his first appearance, he tries to sexually assault Renai in the living world, but is repelled. The second time, he guards the door leading into the Demon's lair and attempts to overpower Josh and take his body. He nearly succeeds in doing so, but through Elise's encouragement, Josh defeats the Ghoul and forces him back into the darkness.

Insidious Chapter 2
The Long-haired Fiend will make another appearance in the sequel.

Appearance
Unlike the other spirits inhabiting the Further, the Long-haired Fiend is actively malicious and has attacked the Lambert family on a few occassions.

His appearance and mannerisms suggests he may have been a criminal in his former life and descended into the Further when he died. As a ghost, his face seems to have degenerated, hence why he is labeled as 'the Long-haired Fiend'.

He wears a black leather trenchcoat, sports dark hair and eyes, and has gaunt, crackling skin.