History of Essence of Insanity

Overview

This is one of the Nightmare Essence quests from Shadowkeep. It is a Eris Morn / Lectern of Enchantment quest: you buy the Essence at the Lectern in Sanctuary on the Moon, cleanse it by completing the objectives below, then return to the Lectern to turn it into gear. Unlike the others, the kills must come from PvE/PvP playlists rather than Moon patrol. Each Essence costs one Phantasmal Core, and objectives only need completing once per account (later identical Essences auto-complete those steps). The quest was part of Season 8 content.

Walkthrough

1. Pick up the Essence of Insanity at the Lectern of Enchantment.
2. Get 100 Grenade Launcher final blows in Vanguard, Gambit or Crucible activities. Defeating Guardians gives the most efficient progress.
3. Claim the Bound Manacle in the Gatehouse: defeat the Hive Knight Ehrath'Ur, Eternal Blade and the manacle drops into your inventory.
4. Visit the Lectern of Enchantment in Sanctuary to create the weapon.

Rewards

Love and Death, a Legendary Grenade Launcher.