It is unknown what exactly the Eternal Collection will contain. With that said, Blizzard is planning to add the Necromancer expansion to Diablo III in the near future. You can check out the ESRB rating summary below:
This is an action role-playing game in which players assume control of a mortal hero (e.g., witch doctor, barbarian, wizard) who must defend humanity from a demonic invasion. From a ¾-overhead perspective, players traverse dungeons/caverns and use swords, axes, flails, and magic attacks to kill a variety of human-like enemies (e.g., zombies, demons, succubi). Battles are accompanied by slashing and flesh-impact sounds, screams of pain, and frequent blood-splatter effects; creatures often explode into bloody fragments as multiple enemies are dispatched at once.
Some levels depict burning corpses, bodies impaled on stakes, piles of limbs, and dead villagers amid large pools of blood. During the course of the game, a succubus creature is depicted topless.
Blizzard previously released Diablo III: Ultimate Evil Edition, which contains the base game in addition to the Reaper of Souls expansion, for the PlayStation 4 and Xbox One.