There are many dogs in the Plains of Dogtur (04.08), particularly in the tunnels revealed by sinkholes. However, nobody is sure where the dogs originate from. Rumor has it that deep within the catacombs there resides an ur-dog, an enormous bitch with a hundred teats, constantly suckling one brood while she swells up with the next.
The Hound of the Underworld supposedly bays for his bitch, the ur-dog.