The monsters in this dungeon are randomly picked from the different tiers of slayer areas, with some special modifiers applied to them, as described in the mechanics below.
Event Mechanics
Starting the event will lock combat content except for the event. You are able to train non-combat skills while in the event, when not in combat. The event's progress is saved. The only way to stop the event is dying or the Stop Event button.
This is a safe death for hardcore characters. Hardcore characters will have normal death penalties, except for the permanent deletion.
The event has 5 stages. At the beginning of each stage, you select a random modifier that applies to all monsters of the current stage and future stages. A random number of 5-8 monsters must be defeated per slayer area, with a harder, "Boss" version being the final monster per area. The Mist Boss enemy passive gives the enemy +20% Maximum Hitpoints, +20% Damage Reduction, -20% Attack Interval, +20% Accuracy Rating, and +20% Global Evasion. The final monster of the final slayer area cleared each stage will be Bane. On the 5th and last stage, the final boss will be Bane, Instrument of Fear. Whenever any Bane spawns, his combat style randomly rolls. Similar to Into the Mist, you must fight him with the SAME combat style as he is immune to all attacks from other combat styles. If you don't want to fight with a particular style, you can run - do not Stop the event as this will reset all progress - and reclear the last slayer area to roll a new Bane spawn. Bane has the same abilities no matter his combat style.
Completing Impending Darkness Event adds Impending Darkness, a lore book, to the bank.
You will get the lore book even if you don't have the space. If you have no slots left, it will simply overflow your bank capacity. This is not true for the shields, but you can repeat the event to get them.