Grim

The Grim was the worst omen you could find because it was a sign of death. It took the form of a spectral, large black dog. It's unknown if it actually was a creature. The Grim was a supposed creature which haunted graveyards. If seen, even in person, it was supposed to be a warning that you were going to die soon.

It appeared in Harry Potter and the Prisoner of Azkaban.

History

The Grim appeared on the cover of Death Omens: What to Do When You Know the Worst Is Coming. A wizard called Bilius saw a Grim and died less than twenty-four hours later.

Sirius Black's Animagus was a black dog which looked like the Grim, causing Harry Potter and Sybill Trelawney to misinterpret sightings and signs of Black for the Grim and thought Harry was going to die. He first saw Black in Magnolia Crescent, a hulking creature which had wide, gleaming eyes. He later saw a picture on the cover of a book.

In September, he had a Divination lesson for the first time where he was reading tea leaves. Professor Trelawney looked in Harry's cup and told him she could see the Grim. He was informed precisely what it was, and Harry had a lurching feeling when he thought back to the time he saw a spectral, black dog in Magnolia Crescent.