Sigil: City of Doors

" A character who takes the full ten-level progression of Demonologist/Pale Master and who reaches a true level of 25 (this includes Level Adjustment) can summon an even more powerful 18-HD creature."

Let's say your character is a Lich(+3 LA) with 10 levels of PM, does this mean you get the 18HD vampire at level 22(as in level that actually shows on your sheet) due to the +3 LA?
Also, wondering if it will make getting level 10 as PM worth it considering welp... everything you gain there you already gain at 10 Lich with the added bonus of not losing yet another caster level which is pretty big on a PM/Lich split.

I'm assuming Alersia used my scripts as a basis for hers, so yes. You'd definitely get the improved demonologist pet.

And you would NOT get this ultimate summon without having the full 10 levels in PM.

Jup. PM is similiar to demonologist.