Valak is a demon that was made popular in the movie The Conjuring 2, Annabelle Creation and The Nun, where Valak was featured as an evil spirit that took the shape of a nun to haunt a convent in Romania, before it was brought to America and interacted with Lorraine Warren of the Warren paranormal investigators. But did you know that Valak is an actual goetic demon?
Valak was first mentioned in the demonology tome The Lesser Key of Solomon, as well as many other demonology transcripts that were written around that time. The Lesser Key of Solomon is actually a book of 72 demons that King Soloman apparently banished during his reign, and how he did it. Valak was listed as the 62nd demon and was described as being "like a Boy with angels wings, riding on a 2 headed dragon". This is a very different image to how the spirit ended up being portrayed in The Conjuring universe, and the nun image itself was a pure invention by the universe's cinematic creator. However, the real Lorraine Warren, who did in fact see the demon Valak, described the demon as a "swirling tornado vortex with this hooded figure", which was how the nun visage came to be.
Valak is also a high ranking official in demon heirachy, not as a king but labelled as a President, and it is said that he can communicate, summon and control serpents in a very He-Who-Must-Not-Be-Named fashion. In summonings, he can give true answers about hidden treasures, reveal where serpents can be seen and "delivers them harmless to the magician". He is said to be able to control either 27 legions or 30 legions of spirits. He is also sometimes known as Volach, Valac, Cooler or Doolas.