Cerberus

Cerberus was a dog-based creature in Ancient Greek religion. In the past he was depicted as a multi-headed, normal-sized or somewhat-larger dog with a snake for his tail and on other parts of his body. Nowadays he is gigantic, restricted to three heads and the snakes are gone. He has a brother, Orthrus. Depending on your interpretation, they might be from the same litter. However, Orthrus is the firstborn. He also has a sister, Hydra.https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0130%3Acard%3D304 They were born from the ageless naga-nymph Echidna.https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0130%3Acard%3D270 In this source, he has fifty heads. 
Cerberus has been depicted as different kinds of breeds. Even in Ancient times the breed Cerberus has been depicted as cannot be agreed upon- he is often a sight hound, but has also been portrayed as low-lying medium-sized burrow hunter (similar to a dachshund) and a larger shorter muzzled breed mixed with a lion. In a Roman mosaic he is depicted the size of a terrier.
Modern depictions always portray him as gigantic, larger than most humans, about dragon-sized. He is often portrayed with the three heads as belonging to the same breed and same color. Often the breed is a tougher sort of breed, such as a Cane Corso. However they may be depicted as other breeds. Rarely is each head a different breed. The middle head is sometimes seen by people as the "lead" or "main" head and may be portrayed as more dominant, putting the other heads in line. Cerberus often appears in works that also feature Hades, as he is his dog.
A man named Cerberus is listed as one of the many suitors for Penelope. It appears that he, along with over a hundred other males, stayed at Ulysses' palace for three years waiting for her to decide who to marry.https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.01.0022:text=Epitome:book=E:chapter=7&highlight=cerberus He was probably killed by either Ulysses or his friends who shot at all of her suitors (and some others). This may suggest that Cerberus is a name that's not restricted to the dog, though whether it was strictly fictional and named after the dog or a real Greek name is not known to me at this time.
== References ==
Category:Dogs in mythology
Category:Snakes in mythology