Do you remember this screaming thing in our fanart Harry Potter Howler Sticker? A howler is a magical letter that is sent in a red envelope and is used to convey a very loud and angry message. When a Howler is opened, the letter itself will begin to scream and shout the message inside, causing embarrassment and humiliation for the recipient. In Chamber of Secrets, Ron Weasley receives a Howler from his mother after he steals a car and flies it to Hogwarts with Harry.