From Halopedia, the Halo wiki
Slavery is the practice of the enforced servitude of an individual or individuals, who are typically treated as property rather than as persons. Slavery is an involuntary condition, and persons subjected to slavery are referred to as slaves or enslaved persons. Slavery has been widely practiced throughout history.
The Covenant and its member species have practiced slavery. Some members of the Covenant, such as the Unggoy and Huragok, were effectively enslaved. In 1112, the Yanme'e were initially incorporated into the Covenant as a slave race. Later, individual Yanme'e known as Unmutuals would be sentenced to work as slaves in penal colonies. The Kig-Yar are known to act as slavers. Following the Human-Covenant War, many Yonhet were sold into slavery by warlords or by Kig-Yar slavers. The Ravaged Tusks were known to be slavers.
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