Army of the Dead

Army of the Dead is a skill in Diablo III.

In-game
This ability revolves around summoning a horde of skeletons to attack the designated targeted area, dealing massive damage to every enemy they reach over a brief time period (roughly 4 seconds).

Skeletons are not actual Pets: they are animated as such, but do not have separate attacks, ignore the terrain and do not block enemy pathing.

Runes

 * Blighted Grasp: Damage type changes to Poison, and damage and duration increase to over  seconds. Visually, the skeletons no longer mass up, but reach out from the ground.
 * Death Valley: The skeletal army knocks all affected enemies towards the center of the area when activated; deals damage over 1 second instead of 4. Counts as Knockback.
 * Unconventional Warfare: Skeletons will rise from the ground and attack up to 5 random targets for seconds, increasing total damage done to  over 10 hits. No longer hits the entire area. Each skeleton will try to find a different target (distributing hits as evenly as possible), but if not enough enemies are in the area, these strikes can all go towards the same enemy.
 * Frozen Army: Damage type changes to Cold, and instead of a circular area, skeletons will march onward as a long wave, hitting all all enemies in a 15 yards wide, 40 yards long line over 4 seconds.
 * Dead Storm: Instead of summoning the Army, surrounds the Necromancer with a blood storm that follows them, damaging enemies within yards for  damage as Physical over  seconds. Adds a  total Life cost.

Non-rune enhancements

 * Fate's Vow (Legendary Helm): Army of the Dead deals 200-250% increased damage and gains the effect of the Unconventional Warfare rune, in addition to its normal effect (with Unconventional Warfare rune, summons twice as many skeletal strikes).
 * Bones of Rathma Set (Set Bonus for 2 items): Necromancer's permanent minions reduce the remaining cooldown of Army of the Dead by 0.5 seconds each time they deal damage.
 * Bones of Rathma Set (Set Bonus for 6 items): each active permanent minion increases the damage of and Army of the Dead by 500%, up to 9000%.
 * Trag'Oul's Avatar Set (Set Bonus for 6 items): Dead Storm deals 3800% increased damage but costs twice as much Life to cast. Healing from skills is increased by 100%.
 * Bonds of C'Lena (Legendary Bracers): Army of the Dead deals 75% to 100% increased damage or double this bonus against an active target of Command Skeletons.

Passives

 * Rathma's Shield: for 4 seconds after casting Army of the Dead, the Necromancer will lose no Life, both from attacks and from their own Blood skills.
 * Blood for Blood: removes the Life cost of Dead Storm rune when picking up a Health Globe, storing up to 3 charges.
 * Blood is Power: every 100% of maximum Life drained by the Dead Storm rune will reduce all remaining cooldowns by 20%.

Development
"For Army of the Dead, we knew we wanted a long cooldown, flashy spell, and I knew we needed a spell to show people how we were going to bring the Necromancer to the next level. We gave it a name from a skill which also exists in World of Warcraft, and people just assumed, "oh, okay, they're just going to copy-paste that." Then we got to show it at BlizzCon, and there were literally over one hundred skeletons on the screen. Is this a world record? It has to be. Seeing the reaction from the crowd at BlizzCon was really satisfying. I'm always looking forward to those moments."

- Julian Love At BlizzCon 2016, the ability summoned over 100 skeletons. As of March 2017, the developers were toying with the idea of a 50 limit, and even this was planned to be reduced, as multiple Necromancers in the same game could result in hundreds of skeletons on-screen.

This spell is named "Skelebomb" in game files.