Four Guardians

The Four Guardians are four powerful martial artists hailing from the time of the Naryu Empire, selected by the Divine Realm, charged with fighting back Dark Chi and protecting the world from the Dark Lord. The heavens granted them immortality, divine strength, and the mystical sword, the Twilight's Edge to protect the Earthen Realm.

History
At the height of the Naryu Empire, the need for Soulstones to power their technologies led to excessive mining, inadvertently creating a bridge between the Earthen Realm and the Dark Realm. As darkness flowed into the Earthen Realm, mortals began to fall to the effects of Dark Chi. To stop the coming of the Dark Lord, the Divine Realm selected the four most powerful martial artists of the Earthen Realm to protect the world: Mushin the Divine Fist, Jiwan the Righteous Blade, Iksanun the Realmwalker, and Hong Sokyun the Earthbreaker. They bestowed upon the Guardians, the Twilight's Edge, a mystical sword with the power to fight off the darkness.

As the demons prepared to summon the Dark Lord, Mushin, in a moment of desperation, sacrificed his life and leapt into the Dark Gate to seal it from within. The remaining Guardians assumed that he would be lost to the Dark Realm forever. They fought the remaining demons but the damage had already been done and the Naryu Empire fell. The world hailed Mushin as a hero for his noble sacrifice and revered the Four Guardians as the protectors of the Earthen Realm. The Guardians became legends through the millennia.

With the rise of the Stratus Empire, Dark Chi began to grow in power once again as the Stratus Emperor's sons battled over the throne. At some point, Mushin mysteriously returned from the Dark Realm however no one took notice of his changed personality.

Thirty years ago, Prince Sogun, with Yura's help, attempted the ancient Divine Mandate Ritual in order to have the Heavens proclaim him as rightful emperor. Yura ensured that the ritual was botched however, as it was part of a larger plot to introduce darkness into the world again. A Dark Gate opened within Highland Central with Dark Chi and demons flooding into the Earthen Realm.

The Sacred Beasts of Moonwater Plains came to contain the darkness within the city. By the time the Four Guardians arrived, the city was beyond saving. They worked together to seal the darkness into the Sealed Palace as a temporary solution to stem the flow of Dark Chi.

Afterwards, the Guardians went their separate ways. Hong Sokyun founded the Hongmoon School at Heaven's Reach. Jiwan took in her first pupil, Jinsoyun. Iksanun continued his travels. All the while the darkness inside Mushin grew.

Current Timeline
In recent years, the Guardians have all but disappeared: Jiwan was rumored to have been killed by her student. Hong Sokyun's declining health prohibited him from teaching as actively. A weakened Iksanun had retreated from the world, supposedly on the run from something. And Mushin was no where to be found.

Jiwan's spirit watches from the Heavens, searching for the hero that would save the world from darkness. She selects the last Hongmoon student as her champion to defeat Jinsoyun, following them throughout, ensuring that they continue their journey.

Hong Sokyun is betrayed by his student, Lusung, and killed trying to save the last surviving student from Jinsoyun. He watches over the hero, ensuring that they do not falter from the righteous path of the Hongmoon Arts. He eventually bestows upon the hero the power of the true Hongmoon Arts to save the world.

Iksanun spends years on the run from Jinsoyun before he is ultimately killed by his own son (through Jinsoyun's trickery).

Mushin still walks the Earthen Realm, to claim his birthright through any means necessary: the Twilight's Edge.