The Black Catalyst Set is an accessory set obtainable from the Dungeon Merchant of the Corrupted Underworld Crypt. Unlike other item sets in the game, this set is only comprised of one item: the level 83 ring "Black Catalyst". While just wearing one ring only provides negative bonuses, wearing two Black Catalysts in both ring accessory slots gives an "invisible" set bonus that's beneficial. The positive set bonuses of wearing two Black Catalysts aren't displayed by scrolling over the set items, but they still appear in the Character Info compass.