Kamdrana

Kamdrana is a plane of perpetual darkness and the incarnation of the inherent evil in the souls of all sentient beings.

Origin and Constitution
Kamdrana is almost as old as the Multiverse itself. As life began developing sentience in the worlds, the darkness of those souls began creating raw energy that began accumulating in a distant corner of the Blind Eternities, giving birth to the plane.

Along with the plane's inception, three Demonlords were spawned to rule over it: Makranos, Malextros and Maukreios.

The plane is exclusively made of black mana, and most of its visitors are unable to give a detailed description of the world, for those who do not wield black mana are unable to see nothing but darkness when they arrive. Even those who do can barely discern the silhouettes hiding in the darkness.

The Demonlords
The three Demonlords were spawned with the plane and, even though they share most of their qualities, they despise each other. Each of them knows that the power of the plane is split equally between them, and if they manage to kill the other two, the whole power of the plane will belong to them. Ever since they were spawned, the three Demonlords are at war with each other. Each has raised an army to combat their brothers, since them being equal impedes them killing each other directly.

The three Demonlords feed on the same darkness that brought Kamdrana into existence, and each has a different way of drawing it out.

Makranos
Makranos is a red-skinned demon with pitch-black hair. He is the first of the three Demonlords who figured out how to project his consciousness outside of Kamdrana by creating a surrogate body out of black mana, thus allowing him to "planeswalk" (-50 NKY). Even though at first he planned to use this power to defeat his brothers, he instead used it to hunt, terrorize and conquer other planes.

His attribute is profanity. He manages to draw out the darkness in others' souls by destroying and ruining what they hold dear, thus triggering rageful emotions.

Malextros
Malextros is a pale-skinned demon. He is constantly secreting a dark mist that reads the souls of the people he interacts with and feeds him their deepest desires. He is the second Demonlord who figured out a way to leave Kamdrana (-15 NKY). Unlike Makranos, Malextros decided to use this talent as a way to kill his brothers and gain ultimate power over Kamdrana. To do so, he travelled to hundreds of planes and began raising horrific armies from the dead of the world. After his forces rose, he left them to subdue the plane in order to grow stronger before the time for the decisive battle for Kamdrana came.

His attribute is desire. By knowing the darkest desires of his victims and offering to make them come true, he brings out their greed and ambition, triggering their will to stop at nothing to get what they want to draw their darkness into him.

Maukreios
Maukreios is a dark-skinned demon with multiple eyes, a couple of horns and no mouth. Unlike his two brothers, he's never left Kamdrana, although whether or not he is unable to do so is uncertain. Instead, he's spent the nearly two millenia of being the only Demonlord left in Kamdrana amassing a massive army and overwhelming most of his brethren's forces.

His attribute is fear. By understanding his victims' fears and threatening to make them come true, he draws out the darkness that the terror of having them come true triggers in them.

Fall
In the year 1638 NKY, the planeswalker known as Pandora arrived at Kamdrana seeking to avenge what the Demonlord Makranos had done to her homeworld (Khaliz-Dorahn). While Maukreios was busy eradicating the spawns of Malextros, Pandora was left to carry on her vengeance unimpeded.

After figuring out the nature of the plane, Pandora used her vindictive desires as a way to channel the darkness of the plane into herself, increasing her power for enough time to deliver a fatal blow to the plane's core, causing a massive disruption to its mana flow.

Even though Kamdrana is virtually indestructible, since as long as there's darkness in the souls of sentient beings it will continue to be, it can no longer empower itself from said darkness, instead using it to stay afloat and prevent its own collapse.