The demon Valac appears in the grimoires Book of Incantations, The Discoverie of Witchcraft, The Lesser Key of Solomon, Pseudomonarchia Daemonum, The Book of the Office of Spirits, The Book of Oberon, and Dictionnaire Infernal
From The Lesser Key of Solomon, Crowley/Mathers edition:
The Sixty-second Spirit is Volac, or Valak, or Valu. He is a President Mighty and Great, and appeareth like a Child with Angel's Wings, riding on a Two-headed Dragon. His Office is to give True Answers of Hidden Treasures, and to tell where Serpents may be seen. The which he will bring unto the Exorciser without any Force or Strength being by him employed. He governeth 38 Legions of Spirts, and his Seal is thus.
The demon Doolas likely a duplicate of this demon.
This demon rides the creature Dragon
This demon wings like the creature Goshawk
Timeline of related events
1536Publication of De praestigiis daemonum (lists this demon)
1563First known appearance of The Book of the Office of Spirits (lists this demon)
1577Book of Oberon completed (lists this demon)
1584Publication of The Discoverie of Witchcraft (lists this demon)
1641Publication of the Lesser Key of Solomon (lists this demon)