Lokarr's Secret Quest

Lokarr's Secret Quest is available on Ultimate difficulty only. There are several steps required, with no attached quest and only cryptic clues given for each step.

The "quest" unlocks the secret Edge of Reality level, and allows the player to fight Lokarr in the Crucible of the Dead.

Guide
1) The quest begins with finding Arcturus - Cursed Smith in Gloomwald. On completing The Gloomwald Stash side quest, he can be found west of the secret area containing Nane's Stash, in a second secret area accessed by passing under some giant tangled roots. There, next to Arcturus, can be found a Rotting Corpse which holds the Turn Back! Note. This note provides a clue for finding the Sanctum: Do not be so Blue in the face. When Flame meets Flame, so shall the way forward be opened...  Arcturus himself can be used to craft the Heart of Darkness, the flavor text to which provides another clue - "Teeming with vile energies that hunger for an ashen altar"

2) This leads the player to the Desolate Wastes, accessed via the Altar of Rattosh. On the northern edge of the area is a stone altar with an Urn next to it. The Urn contains the Mythical Stormheart. The Urn can only spawn if the Heart of Darkness is in the player's inventory.

3) In the Malmouth Outskirts, the player will find, next to the Ruined Shrine, an altar and circle with a blue flame. This is one of the flames referred to in the Turn Back! note. The other is Flameond Bleu, an Aetherial zombie creature who has 3 possible spawn points around Malmouth Outskirts. On finding Flameond, he must be led to the altar next to the Shrine - it is helpful to clear the area first, as other creatures will attack him. Sacrificing Flamond Bleu at the magic circle will open an Aetherial Rift to a secret area adjacent Malmouth Outskirts.

4) There, the player will encounter a Bound Spirit, who will ask for the three objects: Heart of Darkness, Mythical Stormheart and Sahdina's Memento.

Sahdina's Memento can be found in Devil's Crossing, next to the corpse of the Aetherial Colossus lying over Kerrick's destroyed merchant stand. Moving close enough will add the item automatically to the player inventory.

Handing the items in to the Bound Spirit will destroy two of them, but the Mythical Stormheart will be retained. Another Aetherial Rift will be opened, which leads to the Sanctum of the Chosen.

5) The Sanctum contains the You Are Not Welcome! note, which provides the final clue -  Root of All Evil, flourishing in the wake of blood.

Behind the Ruined Shrine in the Sanctum is a Stone Door, which leads to the Edge of Reality. About a quarter of the way along the area is a secret path leading to the Root of All Evil, a creature that, when destroyed, will open an Aetherial Rift to the Crucible of the Dead, where Lokarr can be found.