You need these skills at level 25:

Decompose [1/5]

Enhanced Decompose

Initiate’s Decompose

Bone Spear [4/5]

Enhanced Bone Spear

Supernatural Bone Spear

Blood Mist [1/5]

Enhanced Blood Mist

Ghastly Blood Mist

Corpse Explosion [5/5]

Enhanced Corpse Explosion

Plagued Corpse Explosion

Grim Harvest [1/3]

Fueled by Death [3/3]

Army from the Dead

Prime Army from the Dead

Supreme Army from the Dead

In the Book from the Dead, your class-specific skill tree for necromancers, you select the following companions as well as their skills: 

Reaper Skeletal Warrior: 2. Skill

Bone Skeletal Mage: 1. Skill

Bone Golem: 1. Skill

You need these legendary effects: To play this build, one legendary aspect is especially important, and that is one from the offensive skills. Players can buy d4 gold from a trustworthy shop like MMOWTS to gain access to powerful new abilities and strategies.

Necessary:

Blood Mist: With the aspect of that Blood Mist skill, you automatically cast Corpse Explosions who are around you.

Optional:

Bone Spear: The first hit using the Bone Spear weakened your opponents, and also the splinters cause greatly increased harm to those targets.

Blood Mist: You leave a trail on the floor with Blood Mist, which in turn causes shadow damage. In addition, Blood Mist no more slows you down. Even after all the preparations, if you still need help, MMOWTS.com is here as it offers cheap diablo 4 gold.