Hecate is associated with Sirius the Dog Star. Hecate has a deep connection with dogs and is usually accompanied by a pair of black dogs. Hecate favors dog lovers and the rescuers of dogs. From her mythology, she may manifest as a black dog herself, perhaps the third dog in the image represents Hecate in her animal form. When the moon is dark, and you hear the howling of hounds perhaps you will meet the goddess Hecate.

Illes, Judika. Encyclopedia of Spirits: The Ultimate Guide to the Magic of Saints, Angels, Fairies, Demons, and Ghosts (Witchcraft and Spells). Illustrated, HarperOne, 2009.