Mystery Boss Summoning Key

The Mystery Boss Summoning Key is a wildcard key that opens into one of the four boss summoning keys.

Open it and you'll get one key at random — an even shot at Lamia's Tear, Echidna's Coil, Thanatos' Idol, or Hephaestus' Sigil. Whichever you land on lets you go summon that boss and fight it for its loot.

It only ever rolls the four normal keys. Uber keys are separate relics and never come out of a Mystery Key.

Where to get it: an uncommon find in the Fund II–V lootboxes, from the KOTH Lootbag (5 at a time now, up from one), and it turns up on the Black Market Auction House, from Erebus Pit guards, in clue caskets, rank kits and seasonal crates, and at the Oracle.

Bad-luck protection

Mystery Boss Keys are on the Erebus Guard chase ladder, so you can now set one as your RNG Meter target and let guard kills grind toward a guaranteed one, no need to pull it once first.