Nightmare Essence

Vendor

Base value 15g (carries a vendor price; bought or sold as a reagent).

Crafting

Not craftable.

Gathering

Not a gathered material.

Dropped by

Nightmare Blade	level 50
Nightmare Bowstring	level 50

Note: the monster level tells you the zone tier where it is found; exact spawn coordinates are not published in the game data. See the World Atlas for zone level bands and Dungeons & Raids for instanced drops.