Consualia or Consuales Ludi
This was the festival of Consus, god of the grain stores and councils, who also had festivals on July 7th and August 21st. (His consort Opalia was honoured on December 19th and his August festival followed by the Opiconsivia in her honour on August 25th ). His name seems to be Etruscan or Sabine in origin and relate to ‘crops/ seeding’ (conserere = ‘to sow’). He may have become the god of secret councils from a misinterpretation of his name, from consilium (‘councils/assemblies), not to be confused with counsel (‘advice’).
At this time of year, the harvest was in stored vaults underground. The temple of Consus was also underground, near the Circus Maximus, with an altar covered with earth which was only uncovered for this festival. He was represented by a grain seed.
During the celebration horses, mules, and asses were exempted from work, and were led through the streets adorned with garlands and flowers. Chariot races were held this day in the Circus Maximus, which included an unusual race in which chariots were pulled by mules. Consus was often called Neptunus Equestris (‘Equestrian Neptune’) and seems to be connected with Neptune (Poseidon), the sea god who created horses.
Mars, as a protector of the harvest, was also honored on this day, as were the lares, the individual household Gods.
—Anna Franklin, Yule (The Eight Sabbats)