I do think one of the most horrifying things about Thomas Macabee, is that the narration if his original personality is still there. What do you mean there is sentience and personality left amidst the brainwashing and the horrors. That’s more than a lot of actual necrons. Does that ever get to actually surface?? What horrible psychological mess goes on there??
For those unaware, Thomas was a gue’vesa archeology professor - along with a blank/pariah. Which has interesting implications on how many blanks in human society fail to even make it out of childhood, or live miserable lives if they do - but he has clearly prospered in Tau society. Potentially the Tau themselves just aren’t impacted by the pariah aura and he could integrate with them just fine.
Very unfortunately as a man who is an archeology professor with the resultant love of history and immense curiosity - he ended up on a tau expedition that inadvertently opened up a necron tomb. Everyone else he was with got massacred and he got dragged into the catacombs and turned into a necron pariah - a cyborg, outer shell entirely necron, but having fleshy organs inside meaning they can’t regenerate.
Their minds are entirely shackled but as said above - not gone - which feels almost worst.
Thomas just wanted to teach history and explore ancient ruins and now he’s this, with maybe enough of him left to partly recognise that.