The Essential Details
Once in a while, you'll find a monster encased in crystal out in the world that, when freed and killed, will drop one or more Essences. Essences are special consumable items used for crafting, with behavior similar to an Orb of Alchemy but with guaranteed fixed mods.
That much is covered in the main guide. But Essence mechanics are actually pretty complex, and it's worth pausing to lay them out.
Essences come in various types, seven "levels", and five "tiers". These are relevant mostly for upgrading Essences, covered below; you can't control what types of Essence you find in the world and each of them details what it does anyhow.
Each Essence has a type, indicated by its name (e.g. "Essence of Woe") and its color (each type has a specific color, but see more in the 'tier' section below). A particular type of Essence applies a particular list of modifiers depending on the item you use it on: for example, Essences of Woe apply caster-related modifiers like Spell Damage on weapons or Energy Shield on armour.
The types of Essence are further organized into tiers, indicated by where their icon's color is on the spectrum. The lowest-tier Essences are blue, followed by green, yellow/orange, red, and finally purple. The tier of an essence affects the minimum level it can spawn at, but more importantly it's relevant for using Remnants of Corruption, covered in a separate section below.
The level of an Essence is indicated by its name, which gets "louder" the higher the Essence level is, and by the number of "spikes" in its icon (one per level). The lowest level is Whispering, followed by Muttering, Weeping, Wailing, Screaming, Shrieking, and Deafening. For example, you might find a "Whispering Essence of Woe" (which is a Level 1 Essence) or a "Screaming Essence of Scorn" (which is a Level 5 Essence). The highest level you can find in the wild is Screaming (Level 5), which can be found only in Maps; Shrieking and Deafening Essences are obtained by upgrading lower level Essences.
The higher the level of the Essence, the better the numbers on its guaranteed stat. In general, Screaming Essences are equivalent to the best stats available on normal rares; Shrieking and Deafening Essences go above what is normally possible (but you have to get very, very lucky to get the other affixes to roll well for a good item).
To bring these ideas together, look at the Essence in the screenshot below. Its type is indicated by its name ("...of Sorrow"), its tier is indicated by its color (it's green, so tier 2), and its level is indicated by the prefix ("Wailing", meaning tier 4) and by the number of 'spikes' (4) on its icon.
The simplest way to upgrade Essences is to sell three of the same kind of Essence to a vendor. For example, three Muttering Essences of Woe (level 2) will upgrade to one Weeping Essence of Woe (level 3). This is the most common method for upgrading.
However, the most powerful Essences are not available this way.
Once in a much longer while, you'll find a monster with a Remnant of Corruption imprisoning it instead of an Essence. As usual, free and kill the monster to get the Remnant to drop.
Remnants of Corruption can be used on a still-imprisoned Essence monster to potentially upgrade the Essences attached to it. It can do one of four possible things to the imprisoned monster:
- Immediately release the imprisoned monster without modifying it further.
- Add a new random Essence to the existing list.
- Upgrade the Essences present by one level.
- Upgrade the Essences to random Essences of the next tier.
The last one is the important one, because it is the only way to get the four most powerful Essences.
Corruption Only Essences
These extra Essences are in Tier 6, and cannot drop normally. The only way to obtain them is to use a Remnant of Corruption on an imprisoned monster with at least one Tier 5 Essence attached to them (which can be identified by their deep purple color), then get lucky enough to get the tier-upgrade outcome.
Each of these four essences - the Essence of Horror, Hysteria, Insanity, and Delirium - applies a far more powerful effect than a normal essence would. Most of their effects are unique and cannot be obtained on rare items any other way, meaning these can craft potentially very valuable items and tend to be rather expensive.
In general, you should only use Remnants of Corruption on a monster imprisoned by at least one Tier 5 (purple) Essence, because these corruption-only Essences are far more valuable than any of a Remnant's other possible effects.