Who am I?

I remember the brethren talking about how my self awareness made me a more capable servant than their other animates; that I could use initiative and problem solve rather than just blindly following exact instructions. They referred to me as Shest, I think it was in reference to the number tattooed on my wrist - apparently the cult had tried to create some sort of "smart undead" before with varying degrees of success. The one that I served insisted that it was safe, that I was safe. He said that although I could reason I was... disparate? piecemeal? fragmented? That there wasn't enough memory or personality left to exert any individuality or independence. They believed him but they were wrong.
 
It took a while, I couldn't really understand time then, but there was more of me left intact than they realised. Eventually my fragments came together and I was able to think for myself. I think I was some sort of enforcer or assassin for them but everything is sort of a blur. When I started to speak, started to question... Well they weren't too happy. They decided to kill me, no, kill isn't the word they used because that would've meant they thought of me as alive. They decided to unmake me and then reuse my parts.
 
I acted in self defence and now I am free - but there are still so many questions... What am I? Who am I?