Rune of the Apocalypse is a Death Knight runeforge in WoW, and the public info I found shows it is applied by going back to Acherus / the Runeforge rather than being a dropped item or quest reward. One guide also says to “Apply Rune of the Apocalypse in all content,” which fits it being a standard DK weapon rune choice in Midnight builds.

How it works

The rune enchants your weapon and gives your ghoul’s attacks a chance to apply one of four debuffs: Death, War, Famine, or Pestilence. Those effects are described as healing reduction, increased damage taken from you, reduced damage dealt to you, and a slow plus damage-over-time effect.

How to get it

For the current Midnight-era setup, the usable method appears to be:

  1. Play a Death Knight.
  2. Go to the Runeforge in Acherus using Death Gate.
  1. Apply or change the rune there.

A Wowpedia entry also says Rune of the Apocalypse is a Death Knight runeforging spell available at level 44.

Practical note

If your goal is the exact unlock/source in Midnight, the public pages I found don’t show a separate farmable drop or vendor step; they point to the runeforge application itself. That usually means the important part is having the DK rune available and then engraving it at the runeforge, not chasing a mob drop or raid boss.

Why people care

Midnight guides are already recommending it in Unholy DK setups, which suggests it is one of the main rune choices for that spec right now. The reason is simple: it adds extra utility and pressure through the ghoul- triggered debuffs, especially in content where extra control or target debuffs matter.

TL;DR

Go to Acherus , use the Runeforge , and apply Rune of the Apocalypse on your Death Knight weapon; it is described as a normal DK runeforge effect available by level 44, not a special loot hunt.