Hmmm, on a closer look that Which Can Eternal Lie ability is a bit bonkers, and its kit is pretty strong despite the limited spell list.
Was working with no sleep for 24 hours desperately trying to get a game ready I was asked to do on short notice so I didnt get the best look.
I 'could' adopt it, but Im still working on my dragon, or rather want to work on it but am limited on time and haven't been able to.And I got a few other things I want to build still, despite my lack of free time =P
Still if I actually got around to it, maybe move the resurrection ability of Which Can Eternal Lie to 10th level and get it a bit more on the level of the standard lich.
At first level it can instead keep him alive at negative HP like living creatures can despite being undead and destroyed at 0 then maybe at 5th level give it a auto stabilize at negative HP and a once per day prevent going below -9 HP when hit with an attack that would otherwise have killed it.
That might better represent that endurance to staying alive it wants to have without having straight up free resurrections at 1st level.
Probably remove the free bonus feats at 3rd/6th/9th, Scribe Scroll can stay.
The spells are a bit weird too and very limited. I don't think there is too much issue here for the most part though, at least compared to what a standard wizard will get to have at equal level with it's larger spell selection.
MAYBE change it to be Wizard casting limited to only 1 school instead as the Sphere of Magic ability wants for the sake of simplicity, though that might give it a bit more power then it needs.
Or perhaps keep it as is and give it the option to choose to learn 1 spell from a non opposed sphere every odd level to delimit it's spell list a bit.
It is somewhat odd as a base class, but I don't think it is too far from an alternate Dread Necromancer path into a lichdom style state, albeit it gets it undead portion pretty much immediately =P