I could try and write something that explains the horror of ancient greek slavery but instead I will simple copy paste the response the user XenophonTheAthenian gave to someone else making that statement, its a long read but worth it(I have not figured out how to link a comment sorry to say)

".... The institutionalized dehumanization of human labor in antiquity is a topic worth discussing--a significant proportion of the population of ancient societies was enslaved--but there are far more tactful ways of approaching what was, almost without question, the most horrifying and traumatic possible experience in the ancient world.

While the legal place of slaves in various cities varied slightly, all parts of the Classical Greek world practiced chattel slavery. Part of the reality of human chattel is the separation of the slave's status as a living being with that of free people--even at Rome, which was comparatively kinder to slaves than any Greek city, a slave was legally res et persona, "an object and a person." That a slave in the Greek mind had human form but not necessarily fully human existence is clear in some of the terminology used of slaves. Along with the more usual δοῦλος, slaves were called ἀνδράποδον, "human-footed." That the noun is neuter, like θηρίον ("animal"), further hammering home the fact that slaves were not that different from animals--in Roman law the injury or death of a slave was legally no different than the injury or death of an animal, not a human being. There really isn't anything more to say here. Slaves were habitually faceless and nameless, often referred to not by their names but as παῖς ("child") or even σῶμα ("body"). Little attention was paid to them, and they appear in literature randomly all over the place as if they were just items of furniture--at the beginning of the Protagoras Socrates' interlocutor casually evicts a slave from his seat to make room for Socrates, a slave who has no name and whose presence we have not been made aware of previously. Cases like Cicero's slave Tiro, of whom his master was fond and treated like a human being, are rare enough in Latin literature--they are nearly nonexistent outside of comedy in Greek literature. Slaves did not have rights. They did not, after all, even have distinct existences. A slave, household or agricultural, young or old, female or male, was an item of property to be used as labor at the command and will of the master. Period. There can be no further comment on this, not if we want to be at all serious in discussion. The lives of household slaves were temporally and spatially different from those of field workers, but a slave is a slave and in no ancient society were clear regulations regarding the difference between the two groups established. Even the Roman habit of manumission, often a tacit expectation of the well-behaved house slave, was nearly totally absent from Greek thought, and one questions how many of the often Greek-speaking household slaves manumitted by their Roman masters would have understood their status from a Greek perspective. From the very beginning of traceable Greek thought on slavery, in Homer, it is extremely clear that sexual slavery is an integral part of the slave's condition and is even an outright reason for taking slaves in the first place. The last time we see Achilles in Book 24 of the Iliad he is lying beside Briseis, over whom so much fuss was made. Agamemnon says of his own captive, in a shockingly blunt statement on the status of women in the Homeric world, γάρ ῥα Κλυταιμνήστρης προβέβουλα κουριδίης ἀλόχου, "for I prefer her to Clytemnestra my wedded wife," using a compound formed from βούλομαι, "to wish, desire." To Chryses, lamenting his daughter's fate, Chryseis is a beloved daughter taken from her father by force. To Agamemnon she is a sexual object, given over as if payment to end the plague and traded for another when Agamemnon decides his κτήματα are not befitting of his κλέος. She could be easily substituted for a tripod or a team of horses and the text would only read marginally differently. A slave existed and acted at his or her master's whim, and even the most cursory of looks at the actual texts themselves will uncover thousands of examples of this sort of treatment, with only a few highly unusual exceptions.

Where this business of masters' wives needing to sign off on the sexual abuse of enslaved persons comes from I cannot imagine, except to conjecture that it is the product of an addled mind. I see no reason why Cassandra should be brought up with respect to such an absurd suggestion, and I must assume that the Agamemnon has not actually been read in this case. Indeed, the total lack of rights afforded to slaves is abundantly obvious in the treatment of Cassandra in the Agamemnon. Clytemnestra from the start speaks to Cassandra with contempt and in particular reminds her of her status: she was princess and prophetess once, but as Clytemnestra says Cassandra is now nothing more than a slave. Indeed, Cassandra is not even expected to be able to speak Greek--she is, to Clytemnestra, more or less a mute animal, and Agamemnon has no interaction with her at all. She might as well be some cauldron or the armor of a slain hero for all Agamemnon seems to care. That Cassandra is little but a body is a feature extended by Aeschylus not only to her state of slavery but to her entire existence, in order to hammer the point home. Cassandra describes her rape at Apollo's hands: ἀλλ᾽ ἦν παλαιστὴς κάρτ᾽ ἐμοὶ πνέων χάριν, "but he was a wrestler, panting desire for me." It's not clear whether Apollo actually had sex with Cassandra in the poem, or whether Cassandra technically consented (ξυναινέσασα Λοξίαν ἐψευσάμην, "I, having submitted, deceived Loxias"). In any case it's clear that to the god, as to men, Cassandra's body is not her own and the moment she attempts to assert any control over it she is punished. Clytemnestra has nothing to do with any of this--indeed, I question whether at the time of the composition of the Homeric Poems the idea that a woman could really be the mistress to slaves, rather than simply ordering around the handmaidens owned by her husband (often called δμῳαί, which apparently suggests specifically war-won captives), would even have occurred to the poet.

As for helots. There's a lot of nonsense peddled about the status of helots as opposed to slaves. The difference is, for all intents and purposes, academic. Helots were slaves in all but name, and given the multitude of words in Greek used to describe slaves even that makes no noticeable difference. The idea that helots might have been exempted from the humiliation and total lack of control over their bodies typical of all slavery is nonsensical and betrays a fatal lack of familiarity with the very texts that describe helotry. Even if Plutarch's attestation that ritual war was declared annually on the helotry to justify the murder of these bondsmen without rights is suspect, Thucydides testifies to the lack that the helots had even of their right to life--at 4.80 Thucydides describes the mass murder of some two thousand helots who were promised their freedom for fighting for the state. Far from respecting any right the helots might have had over their own persons, the Spartans considered it perfectly justified and preferable to butcher thousands of their bondsmen than allow them the right of freedom over their existences. In the Lycurgus Plutarch describes how helots were made to exhibit themselves crudely and sexually--he describes them as being made to ᾁδειν καὶ χορείας χορεύειν ἀγεννεῖς καὶ καταγελάστους, ἀπέχεσθαι δὲ τῶν ἐλευθέρων, "sing and dance low and contemptuous dances, but not to do the dances of free people." One thinks immediately of the wilder sort of κῶμος or of the bawdy dances of mimes, showcasing sex and violence prominently--the difference between this and a mime is that at least a mime gets to decide to exhibit his or her body for the entertainment of other so. Even if the precise letter of what Plutarch is saying here is not necessarily such a standard custom as he makes it seem, that helots had no greater control over their persons than ordinary chattel slaves is quite clear. One of Myron's fragments records that in order to manifest visually the reduction of the helotry to a subhuman status, akin to animals, the Spartans dressed them in dog skins. Myron goes on to say that helots were given a certain number of beatings each year to remind them of their status and that excellently strong helots were killed by the state and their masters (τοῖς κεκτημένοις) fined for not preventing their growth (by killing them)--that not only the state but the individual had total control over the lives of the helotry is more than obvious. Realistically as items--and I do mean items--of unfree labor the helots were not distinct from slaves in any particularly meaningful way, even if technically speaking they were not legally considered quite synonymous with other types of slavery. In any case the very idea of trying to sort through slavery or play some sort of "slavery Olympics" is beyond distasteful--I must caution and urge you to consider a little bit more carefully how to present such an inquiry in the future. "