The Dii Novensides were collective deities of obscure significance found in inscriptions, prayer formulary and both ancient and early-Christian literary texts.
It is believed that they held a role in the subterranean world where the ancestors were.
The Vow of Decius Mus
The Novensides were invoked in a list of deities in a prayer formula preserved by the Augustan historian Livy. The prayer is uttered by P. Decius Mus, cos. 340 BC, during the Samnite Wars as part of his vow to offer himself as a sacrifice to the infernal gods when a battle between the Romans and the Latins has become desperate.
Although Livy was writing at a time when Augustus cloaked religious innovation under appeals to old-fashioned piety and traditionalism, archaic aspects of the prayer suggest that it represents a traditional formulary as might be preserved in the official pontifical books. The other deities invoked — among them the Archaic Triad of Jupiter, Mars and Quirinus, as well as the Lares and Manes — belong to the earliest religious traditions of Rome. Livy even explains that he will record the archaic ritual at length because “the memory of every human and religious custom has withered from a preference for everything novel and foreign.”
Digital Maps of the Ancient World 