Valak

Valak is the main antagonist of the 2016 horror film, The Conjuring 2. Valak appears in this movie as a demonic nun.

Valak first appeared during a seance to determine whether or not a demonic presence was truly responsible for Ronald DeFeo Jr. murdering his family in 1974. Lorraine Warren saw Valak in a vision where she relived the murders. This same vision is where Lorraine also saw her husband Ed get impaled. Valak had continued to haunt Lorraine since then.

Later in the movie, the Hodgson family, a family living in the United Kingdom, start experiencing paranormal activity. The family starts witnessing paranormal actibity right before their eyes. On top of that, Janet Hodgson, the youngest daughter, becomes possessed by the spirit of Bill Wilkins, the previous owner of the house the Hodgson family is living in. This makes the Hodgson family call for help and Ed and Lorraine take the case. As it is later revealed, Bill Wilkins had just been a pawn the entire time. The true mastermind was none other than Valak.

Soon after they discover that Valak is behind everything, Ed and Lorraine return to the Hodgson residence, only to find all of the Hodgsons, except for Janet, locked outside. A lightning strike hits a nearby tree, leaving a jagged stump resembling the object that impaled Ed in Lorraine's first vision. Ed ventures into the house alone and eventually finds Janet standing near the window and getting ready to commit suicide. Ed grabs Janet in time, but finds himself holding on to a shower curtain being torn from its rings due to Ed and Janet's combined weight. Soon, Lorraine enters the room herself. She finds and confronts Valak and successfully condemns Valak back to Hell.

Trivia

 * In mythology, Valac is known as the Great President of Hell, with over 30 legions of demons at his command. Valak is said to give true answers about hidden treasures; he reveals where serpents can be seen and delivers them harmless to the magician. Valak is said to appear as a small poor boy who has angel wings and rides on a two-headed dragon.
 * Other ways to spell Valak's name include Valac, Ualac, Valax, Valu, Valic, and Volac.