Essentia

Essentia (Metastasized Essentia) is an item used at the Taken Altar in Eris Morn's apartment in the Last City. It is introduced in the Echoed Warnings quest in Act 1 of the Heresy episode.

Acquisition

Essentia is scattered in random locations across the Nether, and some are hidden in secret chests. Higher difficulties may yield more, so search thoroughly.

Taken Altar

The altar sits between the bookcases and a room divider in Eris's apartment and looks like a totem with a dark orb inside. Ten Essentia are needed to make an offering. Rewards range from powerful legendary weapons to currency and rare materials.