Mold demon

Mold Demons are demons that ate the interior of the Blue Beetle, Harry's VW Bug in Blood Rites.

Description
They were called out of the decay in the Beetle's interior, and then they used anything organic to make bodies for themselves.

Blood Rites
After escaping in the Blue Beetle from monkey demons chasing them after Harry Dresden collects the Temple Dogs for Brother Wang, Thomas Raith, who's driving, asks Harry what happened to his car. The inside of the car had all the seats gnawed bare of stuffing, vinyl, seat covers, chunks of the dashboard were missing, and everything was stripped way down to the metal. Harry had done some make-shift repairs using 1x6 boards, cheap padding from Wal-Mart's camping department and hanger wire to make temporary seats. — Harry says they were a gift from the "guest villain a few months ago".