Diablo 4 has been out for a while now.
When talking about the history of Necromancers in Diablo, we have to talk about the Sin War.
Despite the presence of Uldyssian and his followers, it was merely a chapter, a small one in a saga that links us from the creation of the world of Sanctuary to the present day. One cannot discuss the Sin War without discussing nephalem, for in a way, the nephalem are far more important to the cosmos than Sanctuary, Inarius or Lilith. More important than the Archangels or Prime Evils.