Sparta is the Greek city-state that was the historical home of Leonidas I in Assassin's Creed Odyssey. Leonidas appears in the game's opening sequence, which is set during the Battle of Thermopylae in 480 BCE.
Leonidas was the Agiad king of Sparta and led a Greek force against the invading Persian army at Thermopylae. The battle became famous because the defenders held the pass against a much larger force before being defeated. Odyssey uses this event as a framing story for the family history of its playable protagonist.
Ancient Sparta and Athens are both important in Odyssey, but they represent different political and cultural systems. Sparta was known for its militarized society, while Athens was associated with democracy, philosophy, and maritime power. The game allows players to travel throughout the Greek world during the Peloponnesian War.
Odyssey was released in 2018. Its story is set in the fifth century BCE, well before the historical formation of the Assassin Brotherhood depicted in later franchise chronology.