Horn of Cernunnos is a treasure located underneath the Kingdom of Liones. It is said to be a ritualistic relic that allows the user to communicate with the realm of the Goddess Clan. In reality, it is simply the vessel of a Goddess.
At some point in time, the Kingdom of Liones obtained the artifact and kept it hidden beneath the kingdom for years. After managing to obtain information regarding its location from an unlucky Holy Knight patrolling the room, Ban seeks help from the Goddess, attempting to revive Elaine in exchange for his own life. However, the Goddess decides to only grant Ban's request if he finishes a mission, which is to slay Meliodas, the Dragon's Sin of Wrath.
Meliodas visits the Horn and communicates with the Goddess, who responds that she is unable to continue their fight from 3000 years ago as she is lacking a vessel in which to manifest. The captain of the Deadly Sins confronts her about the lie that she told his comrade and is in turn mocked by the Goddess that he does not have such a thing as comrades in any of the clans, including his own. She taunts him that despite everything he does, those who believe in and love him will leave him when they find out about his sin. The Horn is then destroyed by Meliodas' Hellblaze, while he declares that there are still things that he is willing to sacrifice his life to protect, and that he will continue to fight even if he has to make the entire world his enemy.
- In the "Chevalier de la Table Ronde", Ban is the son of the Gaulois's god Cernunnos who is a great god with Horn.
- Cernunnos is the conventional name given in Celtic studies to depictions of the "horned god" of Celtic polytheism.