About Primordial Angels?

So primal demons will revive no matter what calamity you kill them with - even are getting their core poofed - they will be back again memories and personality etc. intact!! - but what about Primordial angels or seven angels of origin - I mean cornu got one shot by velgrynd and no mentions of him reviving even after a millenia!! also demons are constantly born in hell while angels are not born anywhere?\ So here are my questions:- - Why angels aren't born like demons are constantly born in hell?? (or perhaps spawn is the right term) - Why seven angels of origin cannot come back after death - I mean primal demons can even after getting their core poofed off and with full memories and personality!!