The major characters in the play include:
1. Dionysus - The god of wine, fertility, and theater. He is the protagonist of the play and sets out on a journey to the underworld to bring back Euripides.
2. Xanthias - Dionysus' slave who accompanies him on his journey to the underworld. Xanthias is a comic character who often provides comic relief in the play.
3. Euripides - One of the greatest tragedians of ancient Greece. Dionysus believes that he is the best playwright of all time and wants to bring him back from the underworld.
4. Aeschylus - Another great tragedian of ancient Greece. Aeschylus is already in the underworld when Dionysus arrives, and the two have a debate over who is the better playwright.
5. Charon - The ferryman who transports souls across the river Styx to the underworld. Dionysus and Xanthias have to pay him to take them across.
6. Pluto - The ruler of the underworld. Dionysus and Aeschylus have to compete in a poetry contest in front of him to determine who is the better playwright.
7. Heracles - A hero and son of Zeus. He appears briefly in the play and helps Dionysus and Xanthias on their journey to the underworld.