Baraquiel is a fallen angel of the order of the Watchers, summoned by the group at the Siwa Oasis in Uchronic Paris.
Aby identified him in sources of the Book of Enoch, and links him with a raven in sacred art, a possible symbolic connection to the ravens of Kosovo and the transformation of Corvino. The Sacred Order betrayed him; he fears the companions will do the same. The summoning succeeded, but combat erupted when the process went wrong.
His name sounds more like an angelic name than a raven’s. Gabriel, who forbade time travel, is also present in the gesta; Baraquiel is probably a related but distinct angelic entity.