[ He chooses a rare record of classical music and instead of using magic to put it on he just hands it to Aziraphale. ]

Demons force or trick humans into carrying their offspring, they often do not realize what they are carrying until the offspring is born. We are born with what we call warlock marks, inhuman traits; I have my skin, hair color, horns— [ he wags his fingers, which have an extra joint. ] most warlock children don't reach adulthood.