Gladiator munera
Saturn's chthonic nature connected him to the underworld and its ruler Dis Pater, the Roman equivalent of Greek Plouton (Pluto in Latin) who was also a god of hidden wealth. In 3rd-century AD sources and later, Saturn is recorded as receiving gladiatorial offerings (munera) during or near the Saturnalia. These gladiator combats, ten days in all throughout December, were presented by the quaestors and sponsored with funds from the treasury of Saturn.
The practice of gladiatorial munera was criticized by Christian apologists as a form of human sacrifice. Although there is no evidence of this practice during the Republican era, the offering of gladiators led to later theorizing that the primeval Saturn had demanded human victims. Macrobius says that Dis Pater was placated with human heads and Saturn with sacrificial victims consisting of men (virorum victimis). The figurines that were exchanged as gifts (sigillaria) during the Saturnalia may have represented token substitutes.
Read more about this topic: Saturn (mythology)