Ah Puch is the Mayan god of death, ruling the lowest layer of the underworld, known as Hunhau; he also happened to be associated with war.
When Ah Puch is pictured, he's usually seen with a large body with decaying flesh - his head being a skull or he might holding a skull with a necklace made with eyeballs around his neck or twisted into his hair. He's shown with bells and various symbols of death, such as the vulture, owl or dog.
Even though he is called Ah Puch by Mayan historians, it does not seem to be a valid name for the deity itself.