Who is Raziel from Lamb: The Gospel According to Biff and what is their importance?

Raziel is the angel charged with the task of raising Biff from the dead to write his gospel. He does this and keeps Biff a prisoner in a hotel room. Raziel appears in Biff's gospel repeatedly, once as a black angel who frightens a ship captain to treat Joshua and Biff well. The angel becomes addicted to soap operas and wrestling while watching television in the hotel room.