Mind Flayer Thralls

[Dragannia]

How exactly do Mind Flayers make their thralls? It's never really gotten into apart from a quote which says it takes a long time (I forget which book that quote comes from). I wouldn't think psionic dominate is the key because thralls are supposed to be permanent, and can't really think for themselves. Can someone perhaps enlighten me?

[DoomHat]

I 4E part of the process involves opening up your skull and groping around the insides.

[Inyssius Tor]

In 3.X, I think it's just a lot of mindcrushing.

Newly captured slaves are subjected to inspection and disinfection, followed by constant psychic bombardment to ensure that they become docile and willing thralls. Those lucky few who managed to escape from thralldom describe it as a waking nightmare. The slave is always aware of what he is doing and is filled with revulsion at his deeds, but is powerless to resist illithid commands. The hopelessness and horror of this mental captivity bears down on the thrall as a constant weight.

[Khanderas]

In 3.X, I think it's just a lot of mindcrushing.

Yup, I concur with mindcrushing. Not sure I would go 100% in what the quote says, if it's just a permanent (or recast) domination it would be subject to dispels non-magic zones etc. Illithids are masters at brains and they don't have any morals as we do.
First a proper Dominate psipower/spell to wheel them in. Followed by Charm and back in the lair some illithid speciality mindscrew/mind rape/psionic surgery.
Happy slaves are slaves that don't try to escape. Making them happy to serve and die and even be fed upon by their Illithid masters would make it even more horrifying to me.