One thousand years ago, a massive host of undead swept up from the underworld to threaten the races above. They were beaten back at great cost by a combined force of Men, Elves, and Dwarves know as the Triumvir. The immortal kings of the Dwarves and Elves were consumed and twisted by the wave of undeath. Their kings gone, the Elves and Dwarves retreated from the war, leaving the race of Men to fight alone. The horde pushed the Men all the way back to the walls of their only city.
The gods saw this plight and that their creations were on the verge of being wiped out and became enraged. Veothis ripped material from the sun itself and shaped glowing swords of stellar fire, while Kinat swirled the void together into gleaming black plate armor. Gifts such as these were too mighty to be entrusted to the then immortal race of Men and so a caveat was put upon their use. Only those who would venerate the twin gods would be able to wield the weapons and armor simultaneously, and their use would drastically shorten the lifespan of the entire race that utilizes them.
With the weapons and armor of the gods, the formerly immortal king of Men formed an Order of knights and sallied from the only city to combat the hordes of undead. Their first charge smashed the spine of the horde, killing their leaders and sundering their foe. Only one foe was left, the terrible sorcerer who raised the horde.
In the present day, signs of a massive undead horde are returning, with the races of Elves and Dwarves having retreated into themselves leaving humanity to spread across the upper world. They are unprepared, hundreds of years of religious drift have caused a majority of the Order to turn from the worship of Kinat, offending both and reducing the ability to use the holy armaments to very few.
Humanity is unprepared for a second assault of this size. The world is very close to sinking into the darkness.