The di inferi or dii inferi (Latin, "the gods below") were a shadowy collective of ancient Roman deities associated with death and the underworld. The epithet inferi is also given to the mysterious Manes, a collective of ancestral spirits. The most likely origin of the word Manes is from manus or manis (more often in Latin as its antonym immanis), meaning "good" or "kindly," which was a euphemistic way to speak of the inferi so as to avert their potential to harm or cause fear.
Varro (1st century BC) distinguishes among the di superi ("gods above"), whose sites for offerings are called altaria; the di terrestres ("terrestrial gods"), whose altars are arae; and di inferi, to whom offerings are made by means of foci, "hearths," on the ground or in a pit. In general, animal sacrifice to gods of the upper world usually resulted in communal meals, with the cooked victim apportioned to divine and human recipients. Infernal gods, by contrast, received burnt offerings (holocausts), in which the sacrificial victims were burnt to ash, because the living were prohibited from sharing a meal with the dead. This prohibition is reflected also in funeral rites, where the deceased's passage into the realm of the dead is marked with a holocaust to his Manes at his tomb, while his family returns home to share a sacrificial meal at which his exclusion from the feast was ritually pronounced. Thereafter, he was considered part of the collective Manes, sharing in the sacrifices made to them.
Thus victims for public sacrifices were most often domesticated animals that were a normal part of the Roman diet, while offerings of victims the Romans considered inedible, such as horses and puppies, mark a chthonic aspect of the deity propitiated, whether or not the divinity belonged to the underworld entirely. Secret ritual practices characterized as "magic" were often holocausts directed at underworld gods, and puppies were a not uncommon offering, especially to Hecate.Di inferi were often invoked in binding spells (defixiones), which offer personal enemies to them. The infernal gods were also the recipients on the rare occasions when human sacrifice was carried out in Rome. The ritual of devotio, when a general pledged his own life as an offering along with the enemy, was directed at the gods of the underworld under the name Di Manes.