Barghests — monstrous black dogs.
Barghests appear as monstrous, semi-spectral black dogs with fiery eyes.They're described as large black semi-spectral dogs with glowing red eyes. They're referred to as semi-spectral because while they seem solid enough when they choose to attack, most weapons will simply pass through them as if they were ghosts. They have to be killed by hand or with special magical weapons. ~ Wikipedia
In Shattered, the seventh book in The Iron Druid Chronicles, an army of barghests appear in a battle. They have to be killed by hand or with special magical weapons. ~ Wikipedia