Cerberus

Cerberus is the giant three-headed monster hellhound that gaurds the gates of the underworld.

Behavior
He is very friendly to all who enter the underworld but very agressive to all who attempt to leave. He likes eating, and is very playful.

Appearance
He has a huge black dog body and three heads. His tail is a giant snake, and he is known to have a mane made of smaller snakes

Tips for demigods
If you enter the underworld, he likes to play fetch. He loves cake, so if your trying to leave, cake with a sleeping draft works everytime.