Boss Essence

Boss Essence is a stackable summoning component, the raw material you collect to forge a boss summoning key.

Each of the four bosses has its own flavour-matched essence: Echidna (green), Lamia (purple), Hephaestus (gold), and Thanatos (dark purple), with art that glows brighter as your stack grows. Collect 64 of one boss's essence and the inventory sweep auto-forges them into a single Boss Key for that boss. See Summoning a Boss.

Where to get it: dropped by Shades & Wraiths in the Forgotten Polis, tier-mapped to the boss — Lamia at T1–T2, Echidna at T3–T4, Thanatos at T5–T6, Hephaestus at T7–T8. Lower tiers lean toward the easier bosses; the hardest essences come off the toughest kills. See Hunt Tiers & Boss Essence for the full ladder.

Essence does not drop in the Erebus Pit. Hunting is the only way to earn it, though the Boss Shop will sell you a finished key for Hunter Points instead.

Boss keys stack like any other item, and a stack you split in your inventory or your vault now stays split. The Uber bosses don't use essence at all. Their keys are separate relics that drop from Erebus Crates.