Well idk , i think there's way too little information to say anything.
But I think it is the emperor , only a bit brainwashed.
I don't think his soul passed onto the beyond . I think when they healed him his soul remained but was marooned.
What Shai did was tweak his cognition a bit before leading the soul home.
I think she didn't brainwash him. Not exactly. Ppl change everyday. Sometimes these changes are cumulative , accruing over years or these changes are sudden. For example a near death experience often leads to ppl making major lifestyle changes or atleast changes in how they view life and thier philosophies.
Shai herself states she couldn't just change him into whatever she wants , otherwise the forgery would never take.
She also ponders if after a time , the soul could reestablish it's connection and not require the stamps at all. ( I don't remember correctly , but I think she says that ).
I think ashraven was really dead, they quickly healed him , but like szeth they couldn't heal him quickly enough and his soul got seperated .
What Shai did was use her stamps to basically create a highway for the soul , filled with familiar comforting things to soothe it , back to its mind and body .
I think it is the emperor with regrowth. He's as alive and authentic as szeth or kelsier , only his resurrection method is very different.
Also I don't know what caused his soul to be marooned , I mean szeth got resurrected completely with a little time delay , but then again organic resealing and regrowth are very different , not to mention nalan is way older , experienced and practiced , compared to the resealers of the rose empire who have only a few decades of practice in a mostly shunned art. It was only after the heritage faction came to power that resealing was accepted in mainstream culture .
Hmm yes , I guess that's why they couldn't staple his soul back.
Even in szeth's case , we see that his soul trails behind his mind and body.
I think when they healed ashraven they saved his mind , body and soul. Only they were seperated and the soul couldn't find it's way back.
Shai created a pathway for it and after a while I think the soul will know the path well enough to not need the signs. Ie, ashravan can function without the soulstamp.
On the whole i think it's a better deal than what szeth got.
His soul was stapled immediately but he has to live with that wierd disparity forever ,
Ashraven wasn't healed immediately but he can make a complete recovery .
Slow but steady wins the race.
As for his personality changes. Well , idk maybe he would have done it anyway , near death experiences galvanize a lot of ppl into action.
I think that's what made shai's cognitive manipulation stick in the first place.
So on the whole , i think it is ashraven himself , he's not lifeless , he's not a construct , he's not a cognitive shadow.
I don't know why hoid did what he did . That sounds like a d#@k move , knowing that he would be abandoning to be likely executed and it's not as if he has visions of the future granted to him by Endowment.
Maybe it really was collateral damage , hoid can make mistakes after all.
Or maybe he was forced to abandon her ,maybe a skaze or bloodsealer was hunting him.
Idk. I guess we have to Rafo .
So yeah that's my theory