This mysterious character does not appear in The Angel of Secrets until Dan meets him in a Baghdad Library in Sigil II: The Book of Creation. He had been an advisor to Tania Kosikowski and her daughter Helena, and was involved in establishing the Gallizur Group in 1967, so his name is mentioned in Sigil I.
Barak is a scholar and seems to be a font of great wisdom, but we do not know where he came from, or when he was born. He is exceptionally tall and shows little signs of old age. Could he be one of the nephalim? What can he tell Dan that will help in the quest for The Book of Raziel?
When we meet Barak we know we are in the presence of an illuminated soul who has the capacity to influence events. But he understands the overarching laws of karmic destiny and he is not permitted to interfere in the choices being made by Beth Morgan and Dan Cohen.