Do the githyanki take slaves? It seems out of character for them, but the Psionics Handbook suggests that they do.
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From A Guide to the Astral Plane:
"The githyanki consider personal freedoms and individuality highly important. Their history of enslavement, though long since past, shapes even their current actions and attitudes. Most githyanki would choose death over surrender if defeat meant captivity or slavery. For themselves, they make slaves of their enemies only for short periods of intense humiliation. Slaves're always ritually sacrificed to the queen, eventually."