As you know, the upbringing of the Spartans was very harsh. Science, art, and crafts were not encouraged in Sparta. The land was to be cultivated by slaves - helots. For a free Spartan, such an occupation was considered shameful. Even young men were taught to read and write only within the most necessary limits.
The only thing worthy of a real Spartan was war. From the age of seven, boys were sent to a special school - agela, where the makings of courage, fortitude and obedience to elders were brought up in the child. And from the age of twelve, military education began "in a real way." Young Spartans began to be taught to be cruel and ready to kill.
The first victims of the grown warriors were the helots. Attacks on slaves were called crypts. Moreover, these killings took place legally. The Ephors, representatives of the highest judicial authority in Sparta, declared war on the helots.
Young warriors armed with short swords raided the homes of the helots or killed those who worked in the fields. The ability to sneak up on the victim and send him to another world with one blow of the sword was especially appreciated. They tried to kill the physically strongest slaves. It was they who could raise a riot in Sparta.
But slaves were not always the victims. Despite the fact that helots were strictly forbidden to have weapons, some of them managed to give a worthy rebuff to the attackers. An unsuccessful "hunt" could have ended with the death of the Spartan himself. But, in this case, the fate of the slaves was not enviable. The Spartans sent several detachments to the village, where their comrade died. They cut out the entire village, not figuring out who was responsible for the death of the warrior.
The purpose of the crypti was not only to give young men the foundations of the science to kill, but also to intimidate the helots themselves. They had to live in constant fear. On the example of helots, young Spartans were shown human vices: for example, they gave wine to slaves, so that the young inhabitants of Sparta could see that a drunken man was becoming like an animal.
During the crypts, the Spartans often went to outright meanness. Once, hundreds of helots took refuge from assassins in the temple of Poseidon. The person in the temple was considered inviolable. The Spartans promised to save the life of the slaves, and they, naively believing, left the temple. No one was left alive.
The crypts continued throughout the history of Sparta. The cruel tradition was finally forgotten only after the conquest of Greece by Rome.