World Breaker

The World Break was a colossal world-ending engine employed by the Invaders to corrupt and harvest worlds. In truth, it was actually a colossal corpse of an entity known as the Oathbound Deceiver.

Background
The Oathbound Deceiver was one of the Cathar - beings of terrifying power that harvested planets across the universe to fuel their war against the Demiurge. It was defeated ages ago by the Nine Heroes on Polydeuces and sealed below ground.

Unfortunately for the universe, the Nythyl discovered it, and used the power of its black blood to greatly increase their understanding of the universe. Their entire civilization hinged upon its power, giving them their distinctive black armor and fortresses.

However, the Oathbound Deceiver was not truly dead. Indeed, it was completely without a concept of death, for the Cathar are beings fundamentally opposed to the Demiurges' rules of creation.

The Nythyl should have realized this, making fragments of its soul as "Enslaved Intelligence" servitors in their armies. However, they realized too late, as the Deceiver effectively woke during their final battle on Castores. Had it not been for the great Lightcraft Cannon used by Rouran, the Deceiver could have had the time to fully regenerate and consume the world.

Personality
"The shadow of my corpse will haunt this world for all eternity...."

The Oathbound Deceiver has not been encountered directly, however its whispers have, along with the many fragments of its personality, many created by the Invaders as Enslaved Intelligence. While many of its fragments seem innocent, the main drive of its being is to consume the world and resume its task. However, at times it seems to have given in to defeat, merely enjoying the ruin it has brought to the world that prevented its resurrection.

The Deceiver considers the Nythyl to have been foolish children playing with fire.

Abilities and Notable Equipment
The Oathbound Deceiver is by far the most powerful entity on Castores. Were it to be able to fully regenerate, not even the Gods could stop it. Even so, it may achieve its goal of doing so, should heroes not be able to stop its various fragments from reforming.

As the antithesis of the Demiurge, it is a breaker of rules, hewer of truths, and render of reality. Concepts mean little to it, and it is able to impose its alien rules upon the world. The Invaders power comes from only taping a fraction of its capabilities, even believing it 'dead', they kept it chained with magical shackles...just in case.

Trivia

 * Despite its defeat being a significant event in Castores's formation, it was not added until years in.
 * The Cathar were originally called the Yugoloths, however their name was changed to not be the same as the Neutral Evil D&D monster.
 * The Cathars were a sect of Christianity that disputed who created the universe, and were persecuted by the Church as heretics.
 * The Oathbound Deceiver had a cameo appearance in another D&D campaign that took place technically in the same multiverse.