The Old Gods are the gods of religion and culture that were brought over to America by the immigrants who worshiped them and passed them down through the generations. Some, such as Vulcan and Argus, have accepted the promises offered by the New Gods.
While Shadow is in the Underworld in Chapter Sixteen, Ibis takes Shadow to Anubis to be dissected and judged, leaving Shadow feeling painfully exposed as all of his sins are examined. Anubis asks for Shadow's heart and Bast passes it to Ibis. If Shadow's heart is too heavy, it will be fed to Ammet, the Eater of Souls. Anubis brings out a pair of golden scales and places a feather on one side and Shadow's heart on the other as Ammet lurks in the shadows, waiting. The scale balances out and Shadow is allowed to choose where to go next. Shadow asks for no heaven or hell but to simply rest and let it end. Mr. Jacquel opens a door to Nothing for Shadow, and he walks through joyously.
Bacchus, also known as Dionysus, is the Greco-Roman God of the vine, grape harvest, wine and wine-making, intoxication, fruitfulness, ritual madness, religious ecstasy, frenzy, resurrection, fertility, prophecy, festivals and the arts.
Ganesha is a Hindu god known as the remover of obstacles, the patron of arts and sciences, and the deva of intellect and wisdom.
While Shadow is hanging on the World Tree in Chapter Fifteen, he falls asleep sporadically and dreams of creatures like mammoths and spiders and a giant mouse who an elephant-headed man rides on. The elephant-headed man tells Shadow he should have invoked him before the start of his journey. He performs a coin trick with the mouse (which has shrunk by this point while seemingly remaining the same size) and passes the mouse from hand-to-hand-to-hand-to-hand before revealing the mouse has disappeared. Shadow sees the mouse's tail disappear up the elephant-headed man's trunk and is told to remember that it's in the trunk.
"Hey," he said. "Is there a god with an elephant's head?" "Ganesh? He's a Hindu god. He removes obstacles, and makes journeys easier. Good cook, too."
Gwydion is a Welsh magician, trickster, and hero. His name can be interpreted to mean "Born of Trees". In the novel, he came over to American in the 7th century and works as a stockboy at a supermarket in Humansville, Missouri in Chapter Fourteen.
The Morrígan are three Irish warrior goddesses who are able to foretell the fate of battles. They arrive at Rock City for the battle between the Old and New Gods in Chapter Seventeen. Their arms are covered in blue tattoos, and they wear crow wings on their shoulders and a crow's foot dangling from their necks. The three Morrígna are comprised of Badb, Macha, and Nemain/Fea or Anand.
Bird is one of the Old Gods in the Anansi Boys novel and appears in Anansi tales, where Bird and other animals including Tiger and Monkey are frequently tricked and embarrassed by Anansi. She is a villainous goddess of all birds.
Tiger is one of the Old Gods and appears in Anansi tales, where Tiger and other animals including Bird and Monkey are frequently tricked and embarrassed by Anansi. He is the main antagonist in the Anansi Boys novel and is the god of all big cats, savagery, and the hunt.
Black Phoenix Alchemy Lab created a perfume oil based on the character of Mithras, described as: Oblations of milk, oil, honey, and blood. They also created for their "American Gods III" line a perfume oil based on the Forgettable God: A faint impression of scent, a memory slipping like water through a sieve.
When asked about the "absence" of the Abrahamic God in the novel, Neil Gaiman explained on his Tumblr that technically He was everywhere and yet did not appear as any character of the book - due to the belief that the God of Abraham is "invisible, insubstantial, beyond all understanding, and revealing himself through his works".