I'm confused.
You have a Warlock character that qualifies for 3 PrCs and wish to know our opinion as to which one to choose - or a suggestion on another PrC which you may or may not qualify for?
Just how did you manage to qualify for Green Star Adept, Fiend blooded, and Lich - with a Warlock, none the less?
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Also, wouldn't Fiend Blooded be redundant? You already gain Damage Reduction (due to fiend-like hide developing, I presume), fiendish resilience (Fast Healing a few minutes a day), energy resistance (due to developing fiendish nature), and other fiendish traits due to your warlock character's presumed ancestory.
Neither Green Star Adept nor the 4 level Lich class really do much for your progression in incantations, blast, etc, so I would suggest none of them.
If you do not care overmuch for the loss of incantations, etc, then I would consider suggesting the Lich, as its immunities, etc can stack well with the carefully chosen energy immunities, etc of your character. DR vs Bludgeoning and Magic and DR vs Cold Iron work independently, and Resistance 15 vs Cold can be matched with reisistance vs Fire and Acid, or Electricity and Sonic, or any two of the four prior, making for a nicely resistant character - not even including the resistances that come of being Undead (MAE, Death Effects, Crits, etc).
Still, I have not voted, as I am uncertain as to whether I understand your question entirely.
[Edit] Okay, with that information you provided . . .
I am fully against Green Star Adept (as you would be viewed as little better than an object, or at best a slave of whomever 'owned' the construct that is you).
Lich sounds much better, although I wonder how the Paladin would work with a CE Lich. (Unless your DM has majorly changed things, becoming a lich still requires an evil act.) Even without taking into account the evil aspect, I would think that in a world such as you described the Paladin would be sensing and smiting chaos instead of evil - as chaos is viewed worse than evil. Thus, how is it that you survive? Or have you used an incantation to keep your alignment hidden / altered?
And, again, I have to wonder just what you would gain of taking (a modified version of) Fiend Blooded?