What would you change into?

[Arkham]

Turn into a hamster.

No one expects a Diminutive rodent to fire eldrich blasts from any-ole undefined bodypart...

 

[Sigdel]

I looked at the Lich class, removed quite a bit, added some Warlock things to it, and came up with the below. Note that I consider Paralyzing Touch, Fear Aura, etc invocation equivalents, so they are not gained (nor is the damaging touch, nor are the ability increases, etc). Equivalent invocations can be created for the character to take for those abilities, if the character wishes.

The loss of Con and the d4 HD should help balance this, as should the high cost in xp and gp every other level. I almost also reduced the BAB to low. Casters typically get low, but undead typically get medium. You are not undead yet, but your prior caster class experience - the Warlock - also gains medium also, so . . . I eventually decided to keep it at medium.

I left the name blank [ooo] for now. Somehow Warlock-Lich seems too silly.

All I can say right now is wow. You put alot of thought and work into this. I will e-mail a copy of this to my dm to see what he thinks.
But from what I've seen, very crispy.

 

[Nyeshet]

It might be nice, but understand that it will also hurt a bit.

-4 Con at level 3 is a significant hit to hp (esp considering the d4 HD! ) and fort saves - especially as Fort save for the PrC is poor and you do not gain any additional aid to fort saves till 5th level.

Also, you only gain 2 invocations (presuming Warlock 12 before taking, then continuing till end of PrC). If you decide to take an invocation variant of Paralyzing Touch &/or Fear Aura, that takes away one or both of them.

Otherwise, it is not too bad, and hopefully the bit of DR, Nat armor, and energy resistance will help keep you alive until the fifth level - after which you are immortal so long as your knife / phylactery continues to exist.

Hmm, I just realized I left out the details on that in Undead Transformation (regarding the phylactery). I'll fix that in a moment.

 

[Sigdel]

One of my plans for a potential lich-warlock is the take the eldrich essence utterdark blast and just blast myself if I need some hp.